As others have said, stay away from combat unless you think you can neutralize your enemies this round.
Defensive Blast is probably your best bet before level 8 (when you can take Dread Serpent). The only other reliable combat spell (before level 8 ) I can think of right now is Gelid Bones, but it is a touch spell, and requires both Curses and Oriental.
Ask your warrior friends to do subdual damage in easy encounters, then use Energy Drain and follow with Ritual Sacrifice. If you have 12+ PPs, you should be able to force massive damage saves with DB, whether your enemies save for half or not. Get Opportunistic Sacrifice ASAP, as it will often allow you to get many of the PPs you spent on the DB back.
The beauty of DB is that it's not a spell, so you could wear armor the first levels, and rely on DB and War of Souls in combat.
Unless you need a shield, you should use a staff. It has reach, and allows you to use DB as an "attack of opportunity" in case a dangerous enemy approaches you when it's not your turn. And assuming your opponent doesn't have reach you can move into melee, attack with the staff, and retreat in the same round without incurring Attacks of Opportunity. You might not hit or do any damage, but at least your friends can get the bonus from Multiple Opponents.