>>23043655I would agree with those people, but rotation is still half a year away (August).
Personally I would invest the 20$ or so to play a fun, competitive deck at a local league. Looking online, Empoleon is sold out in all of my known places, but Mew-ex is still in stock.
Night March kind of relies on having Mew as a backup/main attacker, but if you really don't want to buy them the deck is still playable.
If you're just playing at your local league, I can attest to no one at league being hyper-hyper competitive. Even after rotation I can almost guarantee that no one will care if you use old cards at league. Especially if you attend the same one for a month or so, people will expect it when rotation happens.
Good luck, dude.