Or just download the Auctioneer add-on and use it.  Prices can vary a lot depending on the server you're running on, the demand at that particular time, the number of players who are gathering/farming that particular resource, even the time of the week so you need to work out what's best on your particular server - which is where tools like Auctioneer are a godsend.

FYI, when my toons were at that level, I was selling stacks of light leather for 1G MINIMUM, which is a lot for a character at that level with no higher level alts/friends to throw money at him.