Wizard: Easy experience
To easily level up with the Wizard, go to the Imperial Palace level. Towards the end is a room with endless red beasts, and you must find the Magic Key in it. These beasts are extremely easy to kill. Go in to the center of the room and repeatedly use the Path Of Sky attack by pressing A. The beasts will keep appearing, and you will continue to gain experience. This works best with a controller with a auto-fire feature.