I used Zidane,Garnet,Vivi,Freya in my first playthrough, but my standard team is Zidane,Garnet,Vivi,Steiner in my main playthrough. I really like Zidane as a character/fighter, Vivi too. I pick stupid Garnet only because of her Summons, mainly Bahamut who in IX looks fantastic. Else i'd pick Eiko because she is a better white mage and white magic is more important (although i had boosted Mega Flare's damage to max and it rocked, esp in trance). Steiner is there mainly for his synergy with Vivi and his own awesome skills.