When you expend all your MP, it brings up the pink bar, which slowly decreases until emptied, at which point you get a full bar of MP back. If you use something that adds a set amount MP with MP remaining (Ether, MP orbs, MP Rage) it will add that amount to your total, but if you use it with no MP, it will decrease the time left to recharge an equal amount. MP Haste/Hastera/Hastega decreases the time it takes to recharge MP (not sure by how much), and stack linearly. Drive Boost increases Drive gained when attacking during MP charge, and you have an invisible Drive Boost equipped. Berserk Drive lets you use normal hits infinitely during MP recharge (no finishers), though it doesn't count towards Combo Boost. Haven't used the ability much myself, but it can be devastating with some attacks (notably Horizontal Slash).

If you have less MP than the cost to use an ability, you can still use it, and it will put you into MP recharge. This means for Limits and Cure (which always take up all your MP), you're best off using up most of the bar with other spells first, then popping the Limit/Cure with just a bit of MP left (no reason to conserve).

The damage types of KH2 are Physical, Fire, Blizzard, Thunder, Other (Light *Reflect, Magnet, etc*) and Dark *Anti*. Most bosses in Final Mix take full damage from Physical and Other, and half from the others (in vanilla, they took half from Other too). There are exceptions (Demyx is immune to Blizzard, Tifa hates Other). Magic obliterates normal foes (who take full damage from it) and is generally as good or better than physical for bosses with Drives/Summons.

Base Fire, Blizzard, and Thunder all share the same damage modifier for normal and finisher hits (3.0 and 4.5), with Fire being a shade stronger (due to rounding, I'd guess). Fire is an AoE attack that juggles and costs the least of the elementals, but is slower, short range, and hard to spam (finisher has knockback). Blizzard and Thunder are the same speed, with Blizzard being a projectile *with knockback* while Thunder is a long range AoE attack, and the most costly. Fire Boost, Blizzard Boost, and Thunder Boost increase the damage of their respective spells by 20%, and stack linearly. In the Final Mix postgame, you can synthesize Shockcharm+ armor, which has an innate Thunder Boost attached, making Thunder by far the strongest of the elementals.

Magnet gathers all enemies affected into the AoE while dealing some damage and incapacitates them for the duration. Any enemy that walks into the AoE during it is affected likewise. Note that if you hit an enemy affected by Magnet with an attack that knocks it out of the effect (Thunder, Fire, Explosion) it will hit 1-2 times more, per hit. This makes it the best purely offensive spell when it works, and easily justifies its cost (most expensive spell).

Reflect, when used, creates a bubble around Sora, and grants I frames. For a normal hit, if something hits the bubble and Sora does not immediately use Reflect again, the bubble will 'pop' causing absurdly damaging sparks *10.0 modifier, Base* in an AoE with knockback and extremely strong stun. If you use another Reflect before the first one pops, you don't get any sparks, so you can't mindlessly spam the normal hit. The Reflect finisher is no stronger than the normal hit, but you can spam it and as long something hits the bubble, it will go off. Note the strength of the bubble is NOT determined by the strength of the attack that hit it, just Sora's stats. It's also the cheapest spell in the game, and arguably the best.