Do not doubt the knowledge of Agent. He is very knowledgeable when it comes to this game and others. He is right with what he says.
But I’d also like to add the following to my advice — Don’t stick with the same jobs for too long. Learn a few levels and then switch around, mix and match. If you find the right songs, the Bard dressphere is excellent. Keep the enemies occupied with Love Song or Tempt Song and such and pound away. Monk is really good, especially early on, because of the high HP and power attacks. And a summoner’s not bad to have around either, especially if you’re dealing with large groups and you make sure to keep getting the good summons.
Oh, ooh — and have each character be a Chemist at least long enough for them to learn Drink! That way, they can drink stat-boosting potions even if they’re not using the Chemist Job, which could come in handy in a boss fight.