The Drives level up differently. If you want the higher levels of the abilities that symbiotically come with them (High Jump, Dash, Double Jump, Glide, etc) you hafta level up each forme. There's a trick to each forme, and in your stats it will show you points to the next level just like your normal forme.Like I said, I didn't know about this before. I remember reading once some one said you just go fight the heartless to gain more experience. And I guess the chances of getting an Anti-form is less once you get the Final Form and you have 70% supposedly during a boss fight. I'm not sure. I am more familiar with the first game than what I was in the second game.
So basically, just use the drives against anything, right?
Valor: Gains exp for each time you hit an enemy. Just beat stuff up. Pretty straightforward.
Wisdom: Gains exp for each Heartless you defeat. It's best if you spam magic in a crowd.
Master: Gains exp from Drive Orbs collected. Go to places with larger enemies that drop Orbs and be sure to collect them!
Final: Gains exp from each Nobody defeated. Just go to The World that Never Was.
Limit: I have yet to look up anything about it. So I'm clueless.
(I know all this was already covered, but these are my suggestions)
Be in each forme to get the experience (obviously). And if you want to know another trick for keeping the drive bar up: head to the Gummi Ship before it depletes fully. Don't revert, just hop on the ship. This lets you heal AND allows you to play on different worlds regularly.
Lastly: Final Forme resets the counter to get Anti Forme. So just don't use Final for a while and keep going into Drive. Anti will show up more often.