Just got idea how to greatly decrese chance blizz will ban you for gold buying.
1.Buy gold from non chinesee site(aka they understand english nicely)
2. Ask them to do fellowing:
[yourchar]: (to [goldsellerchar]) Hey Adam(put random name here) i just decided to buy my flying mount. could you lent me XXXX(amount you plan to buy) gold?I ll give it back soon
[goldsellerchar]: kk will send it soon
If you are buying from goldseller who wont do that/doesnt understand your english just send ingame mail to char that sended you gold(sth like: Thx mate i ll give it back soon)[you can add: "How is your vacations in china btw?" if you are buying from china website]
Also its good idea to buy 4984gold istead of 5000 for example.. makes it look like your friend is lenting you money.
Hope this helps.. i have never actualy bought gold but i think it would be safer using this method