A good deck using cards from mainly the new sets only would be passmissian/mew. Avoid the mew part if you want (it rotates out), but the deck is cheap and easy to play. If you don't mind a little bit of money spent, try Vikavolt/Bulu, which use mainly new cards and no Pokémon about to rotate. If you are worried about rotation, play expanded, with every card since base set black and white available. You can find a few cards that are cheap in that format. Sorry if this is a bit confusing, and I hope you enjoy the game!