
Originally Posted by
champagne supernova
Or you can create a weapon that converts the limit gauge to experience. One then fights the Tonberry in the Monster Ring (while setting the limit gauge to take damage) and hit the Tonberry with that guy. He should use an attack that deals damage proportional to the number of enemies killed (i.e. a lot) which then gets transferred from your limit gauge to your experience, and allows you to go very far on the sphere grid.
Sorry it's so vague, but I last played X about 3 years ago. But go look at a level-up guide. This method has minimal grind and just allows you to absolutely destroy the Sphere Grid.