Enchanting...
Just got to stay on it. On WoD enchants I get around a 30-50% ROI. Sell 15-20 WoD enchants a day/ 7 days a week. On Tuesdays you sell more. Mats cost less on weekends.
Always diversify your investments. I even invest in potions and elixers on the weekends. Sell them on Tuesdays and Wednesdays. It all adds up.
Keep an eye on the trader rotation. Buy the trade goods when they are off rotation and sell them when the trader wants them. The demand is higher. Thus, the price is usually double the price. Just don't flood the market.
A real gold goblin is patient.