Well I havent tried this, but it seems pretty solid. I just thought about it earlier when I saw a Big Battle Bear on the auction house earlier and felt it could be worthwhile sharing. Personally I have enough gold to not need to try this, but hey.
The basic idea is that now that the TCG mounts are boe you buy a card, redeem the mount and sell it on the auction house. That way "buying gold". Its a process that might just take a while longer than actually buying gold, but it has the potencial to earn you way more gold per $ than normal gold buying.
If you have a look here you can see what the different cards cost. A good try could be the Big Battle Bear or Magic Rooster Egg as the bear cost 120-180$ and the chicken around 200$. And without being sure what it would sell for on the auction house I can only assume it will be a lot considering how much gold most people have stocked up by now.
For the record I seen the bear go for 80 000g. Good luck if you decide to try this. The upside would be no risk at all of getting banned and potencially cheaper gold, but it does as mentioned take a bit longer and a bit more effort. Also the AH takes a cut in yer profit.
This was my attempt of contributing! :wave: