Need some help (no spoilers, just settings)

Hey, just kinda started playing the game, and i have a lottta questions, please help.

1. Quickenings can be used once, once they're used you can't use that quickening for anyone else, which quickenings should i choose for the characters? does that matter?
   When performing a quickening, (i just got the first one), i can't do any of that "chain" stuff where i input combinations for more damage. I don't see any commands that come up or anything except for R2 for shuffle, is this b/c i only have the first quickening?
2. The instruction manual and stuff talk about how you don't always want to have gambits on. Do you guys normally play w/ them on or off? B/c as far as i see it, wouldn't you be better off if you just kept them on, then overrided the gambit by selecting an action through the action menu if you needed to? Your opinions on gambits please!
3. Arethere characters in this game that are especially good at a certain thing? Example, in ff9 steiner was more of an attacker, vivi was more of a magic user etc etc. Just curious as to who i should have as my "set" magic user/healer/physical attacker (unless that's a no go)
4. When you start a big battle or boss fight (or whatever), what would you recommend the best method to set all the protect, haste, regen, shell, etc. Do you have it set in a gambit so that they all do it at the very beginning, or do you do it manually by one person who casts it on everyone while the others attack and stuff.
5. Is there a gambit that you get later so that when someone dies, you can give them like a phoenix down or revive?

You need at least two characters with a quickening to do a quickening chain. The more characters with more quickenings you have, the easier it is to do chains.

Sometimes you might want to turn individual gambits off, but generally it's best to have them on.

Yes. :P Basch/Balthier/Vaan are good at fighting, Fran/Penelo are good at magic, Ashe is pretty good at both. Their individual basic stats and skills differ, but I don't have a list of the exact differences and rankings.

I like to cast support magic at save points so I can fill my MP back up right away.

Yes.