With the release of Sun/Moon around the corner I figured Id post my idea for possible deck in expanded. Focuses on the upcoming eeveelution GXs:
4 Eevee Sun/Moon
2 Umbreon GX
2 Espeon GX
3 Sylveon GX
2 Shaymin EX
1 Computer Search
3 Professor's Letter
4 Ultra Ball
4 VS Seeker
3 Trainer's Mail
2 Dimension Valley
2 Float Stone
Total so far 56
This is what I have so far, just very basic staples/core. Energy needs alot of work since the count seems very high. The general strategy is just to have quick access to the Eeveelutions you want, with Professor's letter helping facilitate that. I think the you can cut one of each of the evolutions but I included at least 2 of each since theres a good chance you may prize one and the whole idea of the deck is to have a toolbox of them. Some following concerns/ideas:
Choice of Stadium: I picked dimensional valley since it allows us to run less Psychic energy for (in my opinion) the least useful evolution Espeon while also allowing us to fight the stadium wars. I feel there could be a better option however.
Lineup of Evolutions: Im not sure what number of the evolutions would be best, Sylveon definitely seems like it would be the one thats used most. Umbreon seems like our main attacker.
Choice of items/trainers: If sylveon being the best one is the case, Im wondering what one-of cards can be used to further widen our toolbox since Sylveon can essentially grab it any time. The whole point of a toolbox is being able to grab things perfect for a situation to swing the game in our favour afterall. Puzzle of time springs to mind, especially if we run finishers to go along with our DCE lineup.
Xerneas: Geomancy seems like a speedy way to get our Sylveons set up, only problem is that maybe we dont need 2 Sylveons and that would use up 2 of our 4 eevees (assuming none are prized).
Energy count: DCE is without a doubt the clincher here, attaching a basic energy of our chosen type to evolve our evee and attaching a DCE to it the following turn seems to be the basic line of play here. The rest however, remains to be optimized. I considered 4, 3, 2 of Fairy, Dark and Psychic but decided to play more to see how things worked out.
General card choices: With so many spare slots and interchangeable cards I wonder what particular direction this deck can take by using different engines; adding in Hammers/Xerosic/FlareGrunt seems to synergize well with Umbreon's GX and Sylveons 2nd attack, Hypnotic Laser/Virbank/Poison barb might do well with Espeons GX attack and Umbreons bench damage. The deck doesn't run a huge amount of ability pokemon so maybe Garbodor could be played. Maxie springs to mind simply because of how popular it is.
Other smaller choices like float stone vs switch are harder for me to make.
Let me know how you guys would improve the deck