Or, you can just eat flax. You might be surprised as how much each sample will restore your magicka.
Yes, and flax is so abundant around Skingrad that you can easily harvest 100 or more. Also, when you eat an ingredient that way, you get a slight boost to your alchemy skill, but not as much as you'd get by mixing the potion. This can be good, if you feel, as some do, that alchemy levels up too quickly; this way, you're only raising your Alchemy skill when you need the effect.
Same thing is true for Cure Disease; there is no reason to buy or carry Potions of Cure Disease, because Mandrake Root is lighter, cheaper, and just as effective as the potion.