it says "All spells are more effective against undead."
Does this include staffs and enchantments?
Is the perk worth getting if I do not use magic too much.

Staffs should be. Beneficial enchantments definitely will if you're a vampire.

On top of that, this http://www.gamefaqs.com/boards/615804-the-elder-scrolls-v-skyrim/63140960 shows all the boosts to perks Necromage offers you if you take Necromage before these.

I can't speak for how useful it is just by itself, but combined with everything else, it definitely sounds worth it.