It is pretty hard on most highly populated servers to make gold fast with anything less than MoP at the moment, if you have the money to invest then sure but it's very very very easy to get banned selling gold on WoW.
I'm really annoyed at Blizzard, instead of trying to keep the players they try to get them to play wow instead...
Feels like they're planning to get most people to go play wow, make them buy expansions & so on. Then in a few months they'll get the players back to d3 with pvp..
if your going to do it the best way is as a hobby, its more fun that way and you will learn a lot more then get getting frustrated there's no money coming in.