I always make my characters like this:
Vaan: Green mage, daggers, med armor
Penelo: White mage, rods, light armor
Balthier: Time mage, guns, hand-bombs, poles, heavy armor
Fran: Black Mage, bows, certain swords, light armor
Basch: Arcane mage, all kinds of swords, spears, heavy armor
Ashe: Red mage (limited black and white magic), staves, swords, med armor