Obviously magicka would be one you want to boost...although with 100% mana reduction at some future point that will actually become worthless in the long run (although at level 40 on my rogue I have yet to get enchanting to where I can get 25% reduction on an item).

Health: Another good one, especially to take a hit or three when mobs close to melee range.

Stamina: Needed to offset the stam cost of dual casting spells beyond novice level.

However, the question I have is there a "best" way to spread your points out as you level up? 1 in each rotating? 2 to magicka and then 1 each, then repeat? Go strictly health and stam and use novice spells until you get the 100% cost reduction? Looking for suggestions as these are just a few of the possible combinations to spend your points.

Pure mage? Two in Magicka, one in Health, leave Stamina alone.

Pure mage I think closer to 80% magicka and 20% health with none added to stamina. Even with zero cost for destruction I like using Dragonhide and paralyze both are costly. I need like 700 to cast DH and I have alteration perked all the way up. I don't have hardly anything in illusion at all, so paralyze costs me a bit too. But that is how I ended up. I am having a blast. Destruction, conjuration, alteration and enchanting primarily.

Edit : the cool thing is there are different ways to do it. Not wrong just different strategy required based on your set up.

I put some points into stamina for extra carry and (more importantly) longer sprint time, especially early on when I have to run away more often and don't have ++carry gear. (Used the Mage stone until Destro hit 100.)

Once Enchant hit 100 there was no real need to put any more points into magicka. Nothing hits me enough to kill me so health isn't super useful either (and a lower health = lower skill Restoration spells.)

OP, the 100% cost reduction will only work for one school, MAYBE 2 if/when you get to 100 enchanting. So unless you plan on only using one or two schools of magicka exclusively, Magicka will still probably be the #1 thing to increase at level up. I found the game incredibly difficult as a pure mage only using 1 or 2 kinds of magic...

My mage is at level 39 and I only level Magicka. Having a really low health is part of the fun of the character, in my opinion. I don't dual cast at all.

Stamina has no effect on casting spells. Running is useful though so you don't want to totally neglect it.

Why are you so set on getting 100% reduction, takes the fun away IMO, just becomes to easy.

I went for 3x 29% reductions = 87%, which is good enough but not over the top. I might add the reduction perk into that as well, resulting in 93-94% reduction.

My sneak mage uses all the schools of magic (no armor), high elf for the magicka and ability, but I still go with stamina a little bit. I use dual wield daggers, or daggers and shield. You might think shields are a stupid choice for sneaky players, but they sync so well with sneak due to the perk that increases the speed with the shield up, likely due to a bug, you can sneak with the shield up faster than you can walk (not run) ha.

But I have quite a strange playstyle.

You can also sneak/run with a drawn bow even when encoumbered.