In order to gain experience after battle, use your stylus to tap the icon of your character. His eyes should now be closed. After defeating enemies, you should see them turn into golden balls. These are your experience points. However, you will not gain any items. If you wish to receive items, tap on your character's face again on the bottom screen with the stylus. His eyes should now be open (Combat mode). After battle, you will receive items, but no experience.