Ok I was dumb when I first started the game. I thought I was being Elite but was gimped. The obvious winners are the default Knight, White Mage, Black Mage, Thief. Cause the upgrades allow 100% of the characters to use every skill perfectly.

In the beginning I used Knight, Red mage, Red Mage, Monk. It got me through the game but these classes are not the best when upgraded. The knight can use some white magic, the thief can use some black magic.

From Best to Worst. (if you used all four of the same class.)

Red Mage - He can attack pretty well and he casts both white and black magic. Independently the Red Mage is perfect to go through the game and succeed.

Black Mage - Also on an all four Black Mage challenge, he gets four chances to cast his powerful magic. He is slow but a great damage dealer.

Thief - If you aren't tough you can run away faster. With an all thief style of fighting you use a lot of potions. He makes training easier when he gets upgraded to Ninja. You can use some Black Magic.

Monk - He can be the least costly but after a while his lack of defense is embarrassing. With all four you got the team that can attack the hardest. I think I attacked Chaos with 1000 damage.

Knight - He is too expensive. He can end fights real quick but the best thing to do is upgrade him to use magic. His high HP and low Magic stat doesn't let his cure spells go too far.

White Mage - This is the class you want to give the best sword in the game to. it has no strength to kill enemies without proper help. The best thing you could do is kill zombies until you level up.