If you want you drive bar maxed, all you have to do, is, Go to the Underworld tournament. Talk to Panic, after talking to him, A screen of all Tournaments pop up.  Go to any one, and once you enter the first battle, Your Drive Bar will be completely filled. Pause, and select quit. When you leave, your bar is still full.  This will help you level up forms and summons quicker.  Also, if you return to the world map while in a drive form you will have a full drive gauge.

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