I played it slightly different to you Killer..
I didn't use any of the spells you mentioned, i just used Healing, Healing Hands and Muffle (to level up).
As for companions I used Lydia until she went missing and then used Aela the Huntress from the Companions for the rest of my time. I gave them both loads of weapons, mainly staffs and let them cause havoc.
As for buying, I did buy iron ignots to make daggers, about 200 in fact, to level up on smithing.
I just got the platinum trophy for this on PS3 on Thursday, after 103 hours game play.