theres hidden drawpoints of the most powerfull spells in the game (meteor, holy, aura, flare, ultima, triples, etc) on both island closest to hell and heaven. you just walk around pressing X and your bound to find them. and they refill quick.

the other hidden drawpoint for aura that i know of is in trabia garden (the area before the basketball court, near the (SPOILER) missle and someone already mentioned seifer, but i think you can refine auras pretty easily. thats how i got them before i fought seifer.