On uesp, looking through some of the various spells (currently warrior, next playthrough will be some form of mage), some of them seem to take a LOT of magika to cast (e.g.Storm Thrall, 991 Magika required). If I am playing a mage, and EVERY lvl up put my 10pts into Magika, I will still only end up with about 900 magika if i play to lvl 81 (which is very unlikely). Are the amounts wrong? Or is there some way to increase your magika without leveling up?? Link is below to see for yourself...conjuration is just an example, true for all mage skills...

http://www.uesp.net/wiki/Skyrim:Conjuration_Spells

I suppose you can get around that by making gear that reduces the cost of conjuration spells.

Perks and gear reduce magicka costs. The perks alone will cut it by half. Then there's also gear that increases your magicka.

Novice, Adept, Apprentice, etc. perks in the magic school's perk trees will cut the cost of all spells of that category in half.

It's probably not enough as many spells are still too expensive even with those perks, but you could also use enchanting which can reduce any spell school's costs to 0, because it's a completely broken and overpowered skill that they apparently didn't ever test before release.