Look people I've beat the game already it took me 3 weeks seriously.
To help you level up fast you have to train but must have bonus battle gauge up. If you can't get your bonus gauge up because the percentage stays at 0%, what you do is you must switch in one of your partners out for someone you havent played with and you must get your bonus gauge up and then switch the three people you want to train keep fighting battles till you have a 15 chain, like you beat 15 battles without breaking your bonus gauge and you'll have all your bonuses {triple EXP} {double FOL} {chance of inreasing HP} {chance of getting an item} so far my Fayt is at level 99 with a little more than 20,000HP/about 2000 MP and at least every attack does 10000 damage my strength is 3000 something and I have the veinslay sword equiped and I want to get the tri-emblem it increases your attack by a 1000.
When you beat the game and you want the tri-emblem try to at least have 6,000,000 Fol yes alot.so far im winning my battles easy and im getting 28,000EXP each time i beat this enemy.
In battle skill on:
{sX}side kick this ones on its max level (10)
{lX}none nothing
{sO}chage this ones on its max level (10)
{lO}air raid (really good) level (8)
and then I have {increase HP damage) this wastes all you cp