Depends. Are you an offensive player? Defensive player? Support?
A good starting school is Balance, they can heal, shield all schools (except tower, just train ice to tower) and their attacks can only be stopped with a tower shield. Balance gets an "all hit" spell earlier than any other school at level 16.
Good starting point to get your feet wet in PVP. They are also a great support school in team play.
Level 5 myth with a double resist, double damage, maycast fairy pet Pack mythblade tc, spirit blade tc, and make sure the pet gives a mythblade Stack all those up also use infallible, then use orthrus is should destroy anyone