What do you need +Magicka for?
If you're Enchanting gear for a Mage it's probably to extremely reduce or completely remove Magicka costs.
I do destruction and +magicka as well. I play a non-armor wearing pure mage, and use 4 schools of magic. It is very versatile. The only school that has outrageous magicka costs is destruction. Using only cloth and alteration spells, means I don't have to spend any points in smithing, in fact the only perk points I have outside of the magic schools are 8 points in enchanting and 7 in alchemy.
I dont like exploits

I don't think 0 cost spells is exploiting, I believe it is working as intended. I'm pretty sure that the developers know that 4*25 = 100. I believe that is why the destruction school doesn't have very high damage output.