I am making a character that uses Dual Wield Bound Swords and wears clothes so he uses alteration for protection.

I will probably have to dual cast the alteration spells, just for the convenience of not having to cast it in the middle of a fight, taking away one of my swords.

Thats really the only need I have for any magicka.

The base 100 magicka is more than enough for two bound swords, but you'll need some more magicka to cast higher end armor spells. At least in the 150 range at higher level armor spells, depending on what perks you choose, skill level, etc.

I'd go up to 300. You most likely don't need to but for convinience alone. Anything higher I'd say is unneeded

I was thinking around 200-250. The dual-cast armor spells are going to be pretty costly. Ill probably take up enchanting, kinda have to with only wearing clothes, but would rather not really use more than 1 fortify alteration enchantment.