Auto-Life is very helpful. I never got it on my own, but it's on the sphere grid. I'm sure Auto-Phoenix is awesome as well... just get 99 MegaPhoenixes and you'll automatically get the customize option Auto-Phoenix to add to any of your parties' armor or weapons. Not sure what you need for Auto-Regen. MegaPotion, maybe?

Break Limit HP would certainly be helpful, but since I had little trouble with a maximum HP of around 6000 by the end of the game, I'd invest in something else, personally.