For much easier xp, and a free portion for each victory, fight Riku before you turn in you rope and cloth and logs. If you chose shield (or sword) as strength at creation, and magic as your weakness this should be no trouble. When he stands back and taunts you, hit him 3 times (he'll parry) and then step to the side. He will do a spin attack, missing you, and you can then do a 3 hit combo on him. It is worth 5 xp for defeating him, plus the potion. If you parry an attack of his it is an extra 2 xp. Just remember, if you use your first potion you will need to equip the new ones you won before entering a new fight. after a few tries or levels you won't even use potions and can start letting them stack up.

But once you turn in the logs, etc. and rest for the night you can no longer fight him, so level while you can!