Still kind of confused about what is and isn't legal to play, I haven't played since D&P Rising Rivals was released.
Trying to get back into the game but what trainers should i have a 4x set of so I can build any deck I want?
M recommendation would be look up some of the World championship decks that won worlds this year. 98% of their trainers are legal (Rotation is Next Destiny and on). Some trainers depending on what deck you build
Some good Trainers I can think of on the spot are N, Professor Juniper, Energy Switch, Energy Retrieval, Skyla, Ultra Ball, Level Ball, Heavy Ball, Rare Candy, Enhanced Hammer, Super Rod, Colress, Ghetsis...
If you want to play Darkrai or any variant that uses Darkness Energies, you'll need 4 Dark Patch. IFyou want to play something Plasma, you'll likely need 3-4 Colress Machine.
4x Prof. Juniper
4x N
4x Skyla
2-3x Colress
4x Ultra Ball
2-4x Level Ball
4x Energy Switch
2-4x Switch/Escape Rope
4x Superior Energy Ret.
2-3x Energy Retrieval
4x Rare Candy
4x Crushing Hammer
2-3x Enhanced Hammer
Those are some of the more popular trainers in some of the most metagame decks, but some of those are a little more specialized towards certain decks, it all depends on the deck you wanna play.