I prefer level up for the unique moves, but I have these "tomes" that teach the user any element moves. I'm not sure where to place them though. Probably either through quests or finding them within the maps- I haven't figured it out yet.
a.mgi + a.atk * 2 + 20
I probably keep messing up the formula, because I forget things and through looking at other heal spells it's a.mat instead of a.mgi, which I have replaced Magic Attack with Magic in the system.