I personally put 45 spirit into this early which helped, but later down the road I found that it didn't seem to matter to much. I never run out of mana, unless I'm using my summon extensively which is going to happen either way, and when resting beside a campfire my mana takes seconds to be full again. So, take it or leave it. I personally would try to hang on the lower side of this stat, and put them into int later