Ill share my toughts.
Genie:
Absolute Domain (yes,you will need it when ppl stun you and aps with will surge)
Expel (not bad to have around as well,if you know how to remove the silence,it can be very useful)
Cloud Eruption (chi skill,all your best skills need chi,im a demon psy,and i need this one,so yeah,i have it)
Faith/Belif (its a must,remove negative effects)
Fortify (immune to stun at possible cost of el ress,this is one of the 'advenced skills'. If you are new into pk,dont get it)
Extreme poison (yes,i have it,nice extra dmg)
Elemental weakness (i prefer it over Enrage and combine with EP)
Enrage (many have it,not my favourite,20atk lvl at lost of def)
Badge of courage (nice to have around to break from stuns)
Pick what you like,also check genie guide here,im sure it will help you.
As for demon/sage. Im demon,simply cause of crits. I crit,i kill.
Sage however lives a bit longer and has that awsome purify at BoL.
EDIT: im on phone,so i cant write as much as i would like.
Mag genie build is nice at start,later depends on skills and playstyle. Also,i was using vit and pdef shards-half half. Till i got +20 vit,now im pure vit sharded.