How old is he? Very often young people will get involved with this type of stuff as a form of teenage rebellion.
My thoughts exactly.
Philosophical satanism amounts to little more than an aggressive and machavellian satanism because most of them dont believe in Gods or Devils either in the sense of acknowledging the existence of such things or placing their trust or hope in them if they do exist.
The religious or spiritual types are different, they range from the mere dabbler to some real sick individuals who would score well as sociopaths or psychopaths, as to whether or not they ever achieve any inexplicable or extraordinary powers, succeed in making pacts with the devil or anything like that, some sources I have read would suggest that some have, while others dismiss that. I, thankfully, have no experience of that.
Most teen satanists I've known are just engaging in totemic or shamanic personal mythologising, like something from The Wasp Factory by Ian Banks, while that book was written by an author who is an atheist and critical of all religion, something missed by many of the readers, I really enjoyed it and believe its a good guide to abnormal or egotistical phases of adolescence.