I think it would be good if you could upgrade spells, perhaps with different upgrade paths too. For example, you can upgrade the arrows to flaming arrows or poison arrows etc. you could even have upgrades to the teleport.
Also it would be cool if you could earn stat points, Attack, Defense, hp, mana etc, and distribute them how you would like to specialise your character further.
Would also be cool if you could combine some relics to create more powerful ones, but maybe they take up more slots if you do.
What do you think?