I'd recommend you choose just one & spend the rest of your perks elsewhere. Also, don't bother getting anything higher than Apprentice Destruction, since you'll most likely end up with Destruction Skill enchants on your gear anyway, which makes magicka reduction perks irrelevant.
Well not irrelevant...after all, you can lower TWO schools of magic to nearly zero (Example: Conjuration for Atronochs and Destruction), but any other spells you cast (Heals, wards, Ebonyskin, Frenzy, etc) will still cost you. It depends on which schools you want to reduce the cost of, and which you just want to use rarely.