I think that answer to this questions is quite easy.
It is one of the most important advertising tools.
So, the best way to use the WAVE3 X-Cards is to distribute them among people.
At such way you can have many potential affiliates, buyers and associates.
Also, don't forget the benefits of being a W3 member: every month you get 5 free TCredits, 50 free MRP's, possibility to win weekly W3 250$ in cash, etc.