I'm playing through this game again (I love this game!), but I am doing A LOT more magic grinding than I normally do. I want to see about how far you need to go before Ultima actually becomes a useful spell. And because I only focused on a few spells on my previous playthroughs, I want to see which ones I can focus on in future playthroughs to make the game even easier.
I'm filling up my mage's magic slots and grinding every spell to at least Level 5. I feel Level 5 is relatively decent for multi-targeting, and I'm hoping it will be enough for Utlima. While this was a pain in the beginning of the game due to the small experience gains from low-ranking enemies, I finally have a go-to spot for magic grinding once Leila and her ship are available. Palamecia Desert has a ton of Rank 5 enemies, and most of them do only simple physical damage and not nasty status ailments to slow things down. Because they are Rank 5, leveling up is pretty easy. Using a Level One spell once instantly gives you seven points, and an additional point per additional use. Level Three spells give you five points and Level Four spells give you four points... plus one for any additional use. It's still somewhat of a chore going from Level One to Level 5, but it's much better than gaining one point for a Level Two spells against Goblins or Bees. It's a great grinding spot if you want to level up one or several magic spells to a decent enough level.
BONUS: Grinding at Palamecia Desert is a great excuse to continue visiting the Chocobo Forest!
I will probably never do this kind of grinding again for this game. But I do want to have a workable Ultima spell in at least one of my playthroughs. It is a major plot point after all.