Anywhere from a few days to a couple of weeks.
Gold trafficking appeals usually takes on the longer side, since they have to go through a lot of potential transactions and logs to see what happened, what might have caused the flag that banned you, etc. You've already given them some information on possible transactions that may have been the cause, but any more detail you can provide always helps.
Also:
I am also writing on behalf of my brothers account which was also banned too and seeing as he was the person that send me the gold his character name was Creepz on nostalrius pvp horde side.
Your brother needs to create his own appeal. They will not check into his account until he does so, himself, in a separate post.