Honestly you would be best going with the commerce app, in combination with this app.
if this plugin does not do what you need.
So using the above your members can earn points for posting etc, or add interest to what they have or Members can send points to other members according to permissions. they can use those point they trade between themselves. from what i can tell users can pay you and get points or currency etc and gift it to other members. Just a thought. As the dev first though to make sure.