Preparing for the final assault
Watch Kingdom Hearts Part 6 from spoonshiro on www.twitch.tv
And now for the most efficient leveling method I know of.
Watch Kingdom Hearts 1.5 - Efficient Leveling from spoonshiro on www.twitch.tv
5050 experience in two minutes was good, but 1008 experience every 10-15 seconds (with two experience-boosters equipped) is definitely nothing to sneeze at. Though it is worth noting that this method is only possible late-game and after earning and equipping the Encounter Plus skill, earned by synthesizing 15 different items Then just equip Goofy with MP Gift and you can do this basically indefinitely.
(I went all the way up to 90 because that's when you learn Second Chance as a mage!)