I'd personally recommend that you make your Red Mage a Sage later in the game, especially if you're playing the NES version. Of course, they nerfed the Sage in the DS version, but I'd still recommend it since it still has more options for magic, though weaker. I would also recommend that you invest one of your characters as a Shaman/whatever the DS name for the higher-level White Mage is (I have forgotten what the name is
) as well.