I love the game! KHII is super fun indeed! But I think they can make the 3rd better if they tried. It has to be longer, and have more cutscenes and have a better control system. I don't like how you have to use your items or summon and drive. They should have made it easier to access. In the middle of a fight, you can't just stop and scroll down with the arrows looking for a potion or something. The enemies would destroy you! But... I know that game is 10 years, so I can't expect it to be perfect now. But they could definitely do better for the third. So, I hope they just give the fans what they want. Without changing the whole game and story of course!
If you're not so satisfied with KH II's control system, I'd assume you'll like Birth by Sleep's control scheme a little better, as there you have no menus to scroll through. Only up and/or down until the ability/item you want to use is selected.
Is there a specific order that I should go about doing the data battles?
Also I'm 2 treasure short of getting them all but they are in the Cavern and it sucks to go chest hunting in there.
Nope, you can try them out in any order you want and start off with the one you can handle the best.
For me personally I started with Larxene, her fight isn't really difficult
like i.e. the Mysterious Figure or Lingering Will, it's just very dragged out because she won't stop spamming her Thunder attacks non-stop for a while and you cannot knock her out of it.
One treasure chest won't pop up until you have defeated all 13 data battles though, so you can't get the trophy for the treasures until then.
Probably not, unless you're in urgent need of a Lost Illusion.
Right, although the first ones to try should probably not Xemnas or Xaldin, as they're arguably the hardest of the data battles.