Ok, so, a good spot to farm AP is on the beaches of Balamb for Fastitocalon-F monsters which always appear in groups of 2 for a whopping total of 6 AP per fight. With the Card ability (best used after whacking a monster a few times) you won't need to worry about beefing up your party too early. It's a great way to learn GF Abilities relatively quick, but there's still a deal of grinding that has to be done using this method. If you get too many cards, just Refine them into Water Crystals, then sell Fish Fins and Water Crystals at the Balamb shop to make room and to get some Gil early on.