Which EX tin should I buy first?

Since it's almost impossible to win on the online TCG because it's so overrun with EXes which EX tin should I start with first? I'm using a customized version of Dragon Snarl, the Hydreigon deck you can buy in stores, which uses dark and psychic energy. Since all of them could fit into my deck which should I start with first? Darkrai, Mewtwo, or Rayquaza?

Mewtwo is vital in tournaments simply as a counter for itself. X-Ball is ridiculously strong if you aren't prepared to counter it.

I'd actually say Darkrai. I'm not just saying this because everyone runs it. It works really nicely with Hydreigon (if you're using the Hydreigon with the ability). Otherwise, it's still good because if your Active Pokémon has a Darkness energy on it, it has free retreat cost. It's attack, Night spear, can 2HKO most EX's as well.

Actually, the only one I wouldn't buy with the deck you're starting with is Rayquaza, since that works better with the Inferno Fandango Emboar or the Dynamotor Eelektrik.