I'd recommend NOT buying gold. It's really easy to get gold nowadays. If you want to maximize goldincome:
Sell the epic gem variants that you don't need for your main's MS or OS.
Do your daily's. Firelands dailys are repetitive as hell, but give good goldincome every single day, when you unlocked most of them.
Tol Barad daily's work as well.
Use your professions to sell some stuff at the Auction House or in trade.
When you have everything from VP, sell VP wrists or boots.
But do not buy gold. Last thing you want to do, and I personally disagree with doing so, as it actively helps out goldsellers, who get their gold from hacked accounts in 99% of the cases.
