I used to think that Fire I,II and III were Fire, Fira and Firaga respectively.
But I remember a couple bosses USING "Aga" spells, in fact I vaguely remember something using "Blizzaga IV" in a fate from awhile go.

So are we just like barely using magic since we can only use I, II and III?

Is there chart I can get a look at for power levels of spells?