I was thinking of something along the lines of an odd sect of Catholicism or perhaps a small Christian denomination that is sympathetic to Catholicism. As a matter of fact my guy would have at least 22 karma in negative qualities. Code of Honor (Shaman's Code) because he thinks he is working with angels and/ or the faithful so he isn't going to try and bind them and force them to do stuff, Big Regret because he did something horrible that eventually led to him having a revelation and becoming a hardcore Christian, and the mouthful known as Pie Iesu, Domine, Dona Eis Requiem due to him seeking repentance from his horrible past and seeing it as one way.
Edit: Hm, if I take Spirit Affinity should I go with Man, Guardian, or Air?
Second Edit: What is the purpose of the Combat, Detection, Health, Illusion, and Manipulation designations for spirits. Did I miss something while reading Street Grimoire?