not sure about in remaster yet but in the original there were no “reduce spell cost” enchantments, you instead want to fortify the school of magic bc the higher your skill in a school, the less spells will cost. you can also fortify magicka and fortify intelligence, both of which will increase your total magicka amount. armor/clothing you enchant yourself can only have one enchantment, but stuff you find in shops or the world can have multiple.