Thanks for the reply.
I didn't think low level conjuration would be useful right now, but I want to know if I level it to 100, I if would be able to perk it, how much magicka I would need, etc.
UESP Page for http://www.uesp.net/wiki/Skyrim:Conjuration
Conjuration as 15 perks, which requires a total of 16 perk points to fill.
5 of those are magicka cost reduction spells, 1 is Overcharge ability which only improves duration and another 1 is simply to increase casting range, but since you have to get the Novice Conjuration perk, only 6 are optional, meaning to fill out Conjuration skill tree (to achieve maximum capability), you'll need at least 10 perk points, so you'll be able to take full advantage of conjuration at level 56 (assuming that you start now)
First, let's see the Master level magics (the ones you'll really want to make use of, since you'll be at very high level) at Skill Level 100, no perks no cost reduction enchantments
Dead Thrall: 590 Magicka
Frost Atronach: 649 Magicka
Storm Atronach: 708 Magicka
Assuming you get Master Conjuration perk, it's 50% from that. 100 points into Magicka should net you 200 magicka (assuming you don't take any Magicka up until this point), so you'll need to take Master Conjuration perk (4 more levels, total 240 magicka) and magicka cost reduction gears (and a handful of Fortify Magicka potion)
Assuming you want to achieve absolute capability (16 perk points needed), you'll net 260 magicka at level 62, still not that much