yep.. what he said.
the best bet you have in getting a high cloud card is to keep buying the packs in all the worlds. if you're lucky you'll get em.
AWWW> now i feel like playing it again. ={
and also.. when you first go to a world, i notice. each new room you go to, there's a chance of getting good cards if you hit items or jump on them..
if you're lucky, you'll get cards, the second time you enter the room it would either be moogle points or HP balls.