Squall is a nice card to have, but ANY Platinum border card (the main characters of the various FF games, basically) are wonderful to have.

Your main objective really should be to get above 60 cards so you can have a deck of 4x***, 1x***** - it changes your chances just as drastically as when you unlocked the ** cards. The GC opponents (there are three, open at different times of the Eorzean day, and you can play against all of them, not just the one of your GC) are like bosses in Triple Triad, they are NOT going to be easily beaten let alone farmed without a dedicated deck.