If you have the spell Silence Daria this will be a piece of cake. When you start the fight, morph into a more powerful form then cast the spell "Silence" so she can't use Mind drain or Minor healing. If you don't beat her right off the bat re-cast silence when it wears off.
Debug Mode and God Mode
Enter the debug mode code at the title menu, a green dot in the top-left of the screen will confirm correct entry. During gameplay on the player 2 controller press Square repeatedly to select the species and press Circle to select level of species, then press X to transform. God mode will give Aleron infinte health, infinite magic and unlock all spells. It must be entered on the second controller during gameplay after entering the debug mode code at the main menu.
To get some easy exp in the castle fight, all the elephants you find they give you a lot of expierience.
Gravestones
In the town behind the houses in the second area is a graveyard. Walk up to each stone and press R1. They will be marked with things such as "Disco" and "Beloved Game Developers".
Potions
In the town after the castle levels, walk behind all the houses instead of on the street. You will find potions a scrolls behind them.