LvL 1-5 quests, Lannergar mine, wolf pelts
LvL 5-10 quests + selling (bad/useless) quest reward items, killing Outlaws arround Freetown
LvL 10+ Outlaws arround Freetown (Bows + Emeralds), Mausoleum
LvL 20+ no idea, but Mausoleum can get you up to 10k, usually ~5k
For Mausoleum, just get high death resistance and shock damage, fire damage works too. I think ice damage is okay too. Keep in mind that the good items (worth 1-2k gold) are in the harder area. There also are a lot of traps, so the best class for this area is the Mage... by far