I always give my characters 2 main jobs that no other chracter uses as well as mastering a few jobs that all the characters use (Thief and Monk)

Bartz: Sword Mage, Knight, Samurai
Lenna/Reina: White Mage, Summoner
Galuf/Krile: Black Mage, Blue Mage
Faris: Ninja, Time Mage

That is the standard set up but I usually give them more jobs to master (I cant remember them all right now)