What Is A Easy Way To Level In Kingdom Hearts Birth By Sleep?

I am Level 40 playing as Terra with Level 4 Dark Haze Fire Dash Blitz Thundaga and Curaga, and level 3 Stun Edge Blizzard Edge and Confusion Strike. I can not beat Xehenort at the end after he takes Terra's Body, So I want to level up but I don't know if there is a easy way to level up besides the way I am. I am currently going back and forth though the Chapel at Castle Of Dreams. My keyblade is Chaos Ripper. Please help