Pokemon Trading Card Game Trainer Challenge Guide

This guide was written to help newcomers out with defeating the tedious Trainer Challenge with as little time and pointless effort as possible. It includes some general tips about the strengths and weaknesses of every free deck, some of the exploitable quirks of the AI and recommendations of which theme deck to buy for Trainer Challenge and custom deck building purposes alike.


Why bother with the Trainer Challenge?
Because you get free cards and tokens for completing the challenge! Every time you finish a game in the trainer challenge, you are assigned a score based on your performance. These points add up, so just defeating the opponent over and over eventually gets you to 4 stars. Once the points reach a certain threshold, you unlock another star. Once you reach 4 stars, you are given a free booster pack. If you do this for every opponent a league, you get 3 additional booster packs. And since there are 3 leagues, 12x1x3 + 3x3 nets you 45 free booster packs! Not to mention all the tokens you get as the 1, 2, 3 star and league championship rewards.
45 booster packs already give you a good start to building your collection, and are basically guaranteed to include some strong and interesting cards. And if you save the tokens to buy a theme deck from the store - not only do they expand your collection by being guaranteed to include certain powerful cards, these theme decks can be used when playing the Trainer Challenge as well, giving you a potentially much easier time there! However, the Trainer Challenge is definitely doable with just the free basic decks.
However, as a new player, you are forced to start with the basic theme decks. And even if you already have codes to in the game to unlock a theme deck instantly, It is still recommended to play a certain number of games with each free basic deck in order to unlock them completely - as a result the cards will get added to your collection and can be used in building custom decks.
The theme decks are pretty awful. However, the AI is even worse, so winning games will be extremely easy once you get the hang of the game, even if tedious. After some games, apart from some very unlucky starting hands, you should be able to win every match by exploiting the limitations of the AI.
The decks
The free deck are the following: Basic Red, Basic Green, Basic Blue and Rallying Cry (The last one is unlocked by redeeming the code "boundariescrossed")
Each deck has different kinds of Pokémon and trainers with different characteristics. Some of the decks work out much better than the others, and knowing what each of the decks excels at is useful for defeating the Trainer Challenge as painlessly as possible.
Rallying Cry is fully unlocked after writing the code, but the others require some playing to fully unlock and power up. Winning a game against 7 different opponents with each deck unlocks them completely, a few cards at a time after every win. After every unlock, the challenge becomes easier, so hang in there.
Which deck to use?
Basic Red
Out of these free theme decks, Red is the strongest against the AI. The Pokémon in the deck deal huge amounts of damage, it has the best search and most reliable draw cards, and many Pokémon in it are great at slowly chipping away at powerful Pokémon to turn even desperate games around. Also, this deck wins games the fastest because of its huge damage potential.
Torkoal is an energy efficient starter that takes advantage of discarded energy while you power up others, Ninetales can mess with the AI using its ability to drag something useless active, and even the lower stage Vulpix can wear down strong Pokémon with guaranteed burn. The powerhouses are Emboar and particularly Blaziken, they sweep very easily once they get going. Last but not least Raticate can destroy anything with the combination of an attack that puts the defending Pokémon's remaining HP at 10 and Rocky Helmet.
Ultra Ball is an amazing trainer and the most important reason behind Red being the strongest deck. Cheren and Juniper are also very reliable draw cards, giving you more chances to get the cards you need to setup. Ether is unreliable but helps get energy into play and at least gives infomation even if it fails, Energy Search helps get energy into play, thin out your deck and shuffle your deck if needed. Energy Retrieval makes up for the discard of Juniper and Ultra Ball. All in all, this is the deck to use.
Basic Green
Green is also a viable alternative, and it should be used against water decks that otherwise would give the Red deck trouble due to the type weakness. It is generally pretty fast to set up, maybe even faster than red, but it doesn't reach the same level of sweep potential.
Bouffalant is a strong basic Pokémon that excels against Pokémon-EX. Against EX-decks, Green can be an equally strong or even better alternative to Red, but Red is always suitable as long as there's no weakness. Serperior can often Sweep thanks to its heal keeping it going even if something hits it back a bit. Try to bench a couple of Snivy and use Level Balls to search for what you need, Patrat can draw you cards to help you set up and Watchog can stall with sleep. Yanmega is nice thanks to its decent attacks and free retreat cost. Beautifly has low priority to get out, it doesn't do much damage and its energy acceleration is very weak, as it only gets one energy every time. Sleep Poison of Wurmple or Harden of Silicoon can buy you turns to power up and draw into what you need and should not be overlooked.
Level Ball is the key to the deck, it helps you get out Snivy and Seviper as you wait for Serperior. Town Map helps you choose what you need from the prizes, but it doesn't help you take the first prize. Colress is a great supporter, giving as many as 10 cards at most. As a downside it's useless without benched Pokémon. Bianca is strong eary on when you can play down your hand to the bench and to evolve, but becomes useless when you can't play down your hand later in game, like Bicycle, and they should be used sooner rather than later. Double Colorless Energy is a very important card to speed up your attackers. It's a viable deck for Trainer Challenge, but the lower damage can make games go much slower than when using Red.
Basic Blue
Blue is the least consistent basic deck. The Pokémon in the deck are decent, but the trainers and supporters are worse than in Red and Green, making slower and less controllable. Unless you can get out the Milotic in the deck to search for any 3 cards in your deck every turn, the deck just gets going too slow, sometimes not at all. And you are only able to search your deck for energy using Cilian, which is weak for a supporter. You can at least use it to thin out the deck, making drawing the right card a bit more likely. Having Feebas draw for you cards using its attack can help speed you up a bit, but with 30 HP and flips, it's unreliable. Lopunny can mess with the AI, but it forces your opponent to switch, which may bring a threat active earlier than you want to face it.
If you get a Lapras going, it can do some damage. The first attach only does 20 for 2, but it can attack the bench, so it's possible to even get KOs without any risk if the AI has something useless stuck active. But the process is really slow that way, paticularly since the AI tends to play a lot of healing, even cards like Pokémon Center or Hard Charms that completely nullify the attack. Probably the best card is Exp. Share, it lets you throw small Pokémon at the opponent's active Pokémon to do some damage without sacrificing energy you have in play in case you have a slow setup, which you probably will.
Another big weakness of Blue is that it doesn't really have any good status conditions. Tympole and Palpitoad could buy you turns, but since the evolution line is thin, losing those can set you back a lot. Milotic's attack is expensive, and if you have a it out, the search lets you set up fast enough anyway.
The plan is to power up Seismitoad or Samurott, but it's hard. The deck only has 1 kind of draw supporter, and it's a rather weak one after taking some prizes, and without proper search cards you aren't able to get the cards you shuffle back in - Great Ball is too unreliable.
I'd just play the required 7 games in favorable matchups to fully unlock the deck, but after that it's better to use Red instead, as Red in a neutral fire-vs-fire matchup is still likely to be stronger than Blue with type advantage.
Rallying Cry
Avoid Rallying Cry. It might look like it has powerful synergy at first sight, but it has no search and very weak draw options, which leads to an awful combination of slow, unreliable deck that requires a huge setup. You will most of the time not be able to get an attacker out, and even if you do, it won't have the full setup to be even half as effective as the other decks.
Outsmarting the AI
The AI has much stronger decks than any of the available theme decks, some of them are full of very strong basic pokémon. However, the AI itself is very bad and has a lot of awful habits that are easy to take advantage of.

1. The AI pointlessly loads Pokémon with way more energy than they can use, leaving the rest of their board empty. This often includes their active Pokémon, in which case you are safe from damage as long as it remains active. Use this situation to your advantage if you have a bad start - power up a few strong Pokémon on your bench before you knock out the opponent's harmless active. Only attack when you have something ready to knock out the opponent's biggest threats. Waiting until you have an Emboar or 2 and a Blaziken, or 2 Serperiors is often worth it if you aren't under pressure, not just make sure you win, but also to maximize your score.
2. The AI switches out low-HP Pokémon, even if they are in the middle of sweeping. So in order to stop the AI from overwhelming you, you don't necessarily need to knock out their attacker - just getting it to very low HP can make the enemy switch to something harmless, and leave that harmless thing active, even if the AI would have been just 1 attack away from finishing you off. It's not guaranteed to work, but most of the time it does. So don't give up, trust in the AI's stupidity. This will become very apparent and predictable over time and should be easy to exploit.
3. The AI doesn't even try to avoid decking out, it uses all search and draw resources possible all the time. Sometimes you can just stop attacking and wait for the opponent to deck out, and win a game with very inferior board position.
4. Some of the AI's Pokémon appear to simply never attack. Even if they have the energy to, they might keep using some kind of a healing move if they have any or just skip the turn. However, this seems to be limited to only a handful of pokémon, like Swanna.
5. Don't get discouraged by a game or two where the AI uses a huge Pokémon EX and powers it up, sweeping everything. It doesn't happen too often - most of the time the EX sit on the bench doing nothing while they power up something completely useless.

Speeding things up

1. Simply put, if you get tired of playing against the stupid Ai and want to be done with the Trainer Challenge as soon as possible, turn off all animations in the options. This makes the game progress much faster.
2. You need to finish less games if you get higher scores. You can inflate your score by attaching as much energy as possible, playing so that you evolve as many Pokémon as possible, drawing as much as possible, doing as much damage as possible, and so on. And ALWAYS PLAY ON HARDEST SETTING. It gives a huge 3x multiplier to the score.
3. Once you have enough tokens, you can buy a theme deck from the store for 500. The decks have some Pokémon that are much stronger than the ones in the basic decks, but might not have as impressive supporter lines. Certain decks are particularly consistent and include certain extremely strong cards, though, and can make the Trainer Challenge much more of a bearable experience.

Putting your tokens to use - the not-so-free theme decks

1. DON'T BUY FENNEKIN, FROAKIE OR CHESPIN DECKS. They are awful and not really meant to be playable, they are full of cards that are made for little kids as their first cards or something and don't meet the standards of the game at all. The decks include no good Pokémon and awful trainer lines, as well as way too much energy. There's literally no benefit to buying them.
2. INSTEAD, buy some of the other decks available. I recommend the following two first and foremost:

Resilient Life - Has the makings of a good Fairy-type deck. Xerneas is great at getting energy into play, and also a very decent, bulky attacker for a basic. The support Pokémon, Aromatisse and Slurpuff, help you keep energy in play and give you a huge advantage in some matchups by giving immunity to special conditions. Mr.Mime is also decent, and Dodrio is not too bad at doing damage. However, the psychic types are very weak and the includes some useless, incomplete evolution lines that are waste of space. The draw and search cards are pretty weak, which makes the deck slow and unreliable - you won't necessarily get the amazing Xerneas - Aromatisse combo going.
All in all, the deck includes some very useful Fairy-type cards that can overpower the Trainer Challenge if they set up with their flexibility, but the slow setup stops it from being too overwhelming. Red and Green decks might still be better thanks to their better search and draw options, but this is definitely a good deck to buy if you are interested in a Fairy-type deck - or a toolbox with various different types taking advantage of Rainbow Energy and colorless attack costs!

Dark Hammer - Seems to be by far the strongest deck in the Trainer Challenge. It include 2 Sycamore and 2 Korrina, both of which are amazing supporter cards. They cover search and draw very well. Machamp and Landorus are very useful Pokémon in a fighting deck, particularly the Landorus. The energy acceleration potential is pretty low due to only having Sycamore to discard, but Landorus is still a strong basic by Trainer Challenge standards. Even the Mienshao can be used in a lock deck. Sycamore is great addition to your collection, just like Korrina and Evosoda. And this deck has no incomplete evolution lines whatsoever. This is easily the strongest deck for Trainer Challenge, and has some very useful cards for a fighting deck.
Dark Hammer and Resilient Life are the top 2 candidates for theme decks to buy with your tokens. Dark Hammer is slightly stronger in Trainer Challenge but Resilient Life includes all fairy support in one package. What it comes down to is if you are more interested in a fairy deck or a fighting deck.

Finally, there are free card codes you can enter. Use these codes for a water/normal Rallying Cry deck: FlashFire, PlasmaFreeze, FuriousFists, PlasmaBlast, PlasmaStorm and BoundariesCrossed.  

You can also enter DarkExplorers, DragonsExalted or NextDestinies for a Pokémon EX Hat.  

Most of what I wrote in this guide is pretty obvious, but hope it was helpful and worth a read to someone.