Combination of a lot of different ideas like selling the gems, bumping sagecraft, detect hidden and mercantile skills being a few along with participating in as many sidequestsside quests as possible all iI would echo as recommendations.
But one that I haventhaven't seen anywhere is Rose Barden and dice roll Gamble at the Star Camp in the Sidhe .
She will bump into if you hang around the camp long enough unless she's asleep on a blanket somewhere in the camp. When she offers you a roll of the dice, save then take the bet.
Obviously if you win save your game and repeat, and if you lose exit and re-load from the save point.
Save after each win and if you are patient enough 10-12 rolls you can make about 4,000.00.
Yes it takes time but it is a sure win as long you remember not to save when you lose and only save the positive results :).
There are other trainers in the area as well as a buy sell merchart and that 4,000 bucks could pay off for training in stealth and mercantile I believe or getting health potions and recipes whichwhich you always need to survive and progress in the game.