. . . the quest to promote monk to initiate, given by Bartholomew Hume in the little village south of Harmondale. It involves clearing the tombs in the Barrowdowns, which will give you some useful experience. I remember doing that one fairly early on. You can retrieve the Lantern of Light (see Tarin Withern in Harmondale) at the same time.
You might also try the Paladin to Crusader promotion quest. Killing a dragon at your stage sounds horrendous, I know, but Wromthrax isn't really all that tough. Try and weaken him from range — a few effective wands might prove useful here — before you close in for the kill. Save first, obviously!
You can also get experience from killing monsters, so a bit of exploration would probably help.