Floating Continent: have 3 Red Mages and 1 White Mage, or even 4 Red Mages if you want. The early jobs all suck, but Red Mage surprisingly is good since they can physically attack and also cast limited healing and attacking spells. Red Mage of course will be made obsolete by later jobs.
Alternatively, make Refia a Thief and have her in the front of the party so she can pick locks. Have one guy be a dedicated White Mage.
Once you get the Fire Crystal jobs, a Scholar might be useful to detect Hyne's weaknesses, and consider changing 2 of the Red Mages out for a Knight and a Black Mage. A Geomancer may have limited use with the ability to cast Geo-magic for free.
Once you get the Water Crystal, train 4 Dragoons immediately for Garuda. Thereafter you might as well keep 2 Dragoons, or change them into Dark Knights if you prefer. Change Refia back to a Thief, and have 1 dedicated White Mage.
Once you get the Earth Crystal, train 2 Ninjas and 2 Sages. During the final boss battle, your 2 Ninjas will be throwing Shirukens while the 2 Sages heal every round. And of course, you might need Onion Knight if you're going to do the optional superboss.
If that's what works for you. Why suggest a certain character be a certain job, though? They're all identical.
And the early jobs don't suck at all. Warrior is very good, one of the best physical attackers in the whole game.
Black Mage is one of the best jobs in the game, hands down the best job early-game. Yes, it gets outclassed by Magus in the last 10% of the game or so, but so what? They help you get there more quickly. And your job level would be so high that you'd have to grind for a few hours to even make Magus as good as Black Mage.
Red Mages have pretty pathetic MP, so White Mages make better healers as well. I only found Red Mage to be useful up until around the fight with Salamander.
Monk is arguably better than Black Belt, since Retaliate is infinitely better than Boost.
Thief is good too, for what it is.
I never even touched Ninja or Sage, and I got along perfectly fine at the end game, I never got stuck on a boss.
Besides, if you're that worried about the final boss, just get four Scholars and use your Chocobo Wraths, the battle will be over in one turn. Getting extra Chocobo Wraths isn't much more impractical than farming gil for shurikens, either.
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I don't know why you'd recommend Red Mages, I've used one in every playthrough so far and I'm always left disappointed by their meager physical strength and poor MP. Then again it really doesn't matter what jobs you use until the Salamander boss, I guess.