I'd recommend full Mind. Piety helps, but you need a lot more than 30 points to make a difference in your mp pool.

At level 32, you will just have gotten Freecure. Make sure you are using Cure I as much as possible and Cure II only on Freecure procs unless absolutely necessary. At level 34 you'll get Stoneskin, which you should probably not use too much during combat until level 50 - it will TANK your mana very quickly. At level 35 you'll get Regen, which is a ridiculously efficient single target heal, albeit a slow one. Keep that on your tank as much as possible and you'll do great. Then at level 38 you'll get Shroud of Saints, which will help your mana a lot.

Basically, you're at one of the low points in WHM MP management (just past, actually, since you have Freecure). The other ones will come around 47 (Shroud hasn't updated yet and Aurum Vale is hard on mana), and when you first hit 50 and haven't yet gotten higher level gear but are still expected to heal like it in starting raids. If you can make it through those times, you'll do just fine.