For starters, I really like the idea of this game and the sprites and interface are very nice.
However, you really need to revamp the combat. The way it is now it is mostly just doing the same button over and over again to win.
The first thing I would suggest is expanding your character's skill set. Not just by adding more Skills to everyone except maybe Lucy, but to make the skills more unique.
When I used Aries I hoped that it would be either a shield, a heal, or a buff. However as far as I know every skill is a damage skill, so there is no reason to use anything except the skill that does the most damage. Natsu and Grey basically have an attack that costs Mana since I don't think you have any Elemental effects. Erza simply has no skill at all.
Try working with Buffs, Heals, Debuffs and Damage skills that have varying effects based on the situation, so that you can choose different skills for different occasions.