I recommend plan build in Arena Test mode.
Stealth really nice early on to steal stuff. Element and arcane tree skill are most of my dmg come from. Blood magic passive skill neat to hp regen. Theres oblivion potion can buy to reset skill point in case want to change.

Just started it, game seems great! Any spells/skills you recommend investing in that are particularly useful? So far I've put a few points into melee +dmg, stealth, and raise undead minion spell. Only level 4 or 5 right now.