Once I got my constitution up a bit and got equipment with health / mana bonuses, I started mostly concentrating on strength and agility. Agility effects your chance to hit and your chances of being hit. At the start you need strength to equip the better armour and weapons, but once you meet the minimum requirements, get your agility up as well. If you get the first hit in, it can make a big difference in the fights. See
differences between classes for secondary stat calculations.
At least the first level of Repair is very handy, and almost required.
