So I've been playing with enchantments, and I got to wondering. If at level, let's say, 25, you had the option of creating an enchanted item that fortifies destruction (or another magick skill) 12%, or increastes total magicka by 50, which would you choose? I've got two items right now that reduce my magicka cost for destruction by 27 (15+12). I can create another +12% reduction item, or use a hood (adept) that increases total magicka by 50...which would be the best option?

Well, I guess the question comes down to what spell you cast the most and how much magicka it would save you. How many more spell casts would it get you vs an extra 50 magicka?

Another thing to consider is that a reduced spell cost means that if you go OOM, your wait before you can cast again will be shorter.

I'm not sure what OOM means.

Out of Mana/Magicka.

On a slightly related note, I've often wondered. Is magicka regen based on a percentage or stright number?

It appears as if it's percentage based.

The more you have, the faster it regenerats.

I guess that does complicate things a bit, then.

how about fortify destruction damage? Oh wait it doesn't exist...

You regenerate a percentage of your magicka per second. So the higher your maximum magicka, the more magicka points you regenerate. It's helpful to all of your magic as well, not just a single school. Only problem is, in Skyrim, magicka regeneration is cut down to 33% when in combat. In Oblivion, i was able to get my Breton Spellsword up to like 700-800 Magicka with Fortify Magicka enchanted gear, and she could spam Master level spells without a care, because casting them took so little of her magicka pool that she regenerated it almost as fast as she cast them.

Fortifying 100% of destruction makes every single destruction spell you use completely free.

Not only does this already give you a huge advantage, it also saves your MP pool for other schools.

Fortify Magicka will increase your MP, but it's still gonna run out if you're not careful, while fortify destruction to 100% will make you an elemental turret.

The best option is to create two items that reduce costs by +12% Not kidding, you should be able to put cost reduction enchants on 4 armor parts total and you only got 2/3 it seems

Anyway, answer to your question is hard because we kinda lack information. First, how much base magicka you got already? If you only have 100, then the +50 effect is probably the best for now. I'd say, go for the enchant that allows you the highest number of spell casts in a single magicka bar with the advantage for cost reduction if it goes somewhat even because it also saves you magicka pots in the long run : casting two nukes at -50% for a total of 200 magicka is better than cast two nukes at -0% for a total of 400 magicka because it costs you fewer pots to restore it It makes you more vulnerable to shock damage drain though.