It is not against the rules to sell gold, at least not stated on the rules page. Also I don't see anything wrong with advertising it, as long as it stays in the advertisement channel, where you by the way cannot even spam (like dyablo said). As soon as you start to spam your services for advertising purpose anywhere else it will violate the rules more clearly.
However, selling gold is not one of the three points being stated in the rules page so it can lead to a punishment but I don't see how you can be able to spam in advertisement channel. At least my opinion is that you're alright, I don't see what you did for something illegal.