For the spells, I'd recommend something to cure (better elemental spells for Ifrit, Ixion, Shiva; Cure/ra/ga for others) and maybe some buffs. I dunno... all the upgrading I EVER did was teaching Curaga and Haste to Anima, and that was it. Stat upgrading doesn't pay off anyway, it's much faster to just level up Yuna.
Besides, right now, Bahamut pretty much owns everything anyway, you don't need anything IMO.