If you talk to the trade wanderer and then click the Help  button to get more information, it brings you to the village trader articles rather than a wandering trader article. This is actually really bad because those articles say that you can do bad trades with traders in order to level them up to get better trades. This is not true for the wandering trader who does not level up or change his trades as a reward so I almost spent Emeralds on things I didn't want to gain exp/reputation with him until I decided to google it first.