I am looking for a setup where a user can sign up to my

Hi,

I am looking for a setup where a user can sign up to my site, become a free member, and be presented with a list of actions that he/she can choose from. An action could be: "Please sign up for this questionnaire and get 100 points".

After completing a chosen action, the user will then be awarded a certain amount of virtual currency/points and that can be exchanged for cash later on.

What combination of plugins do you recommend that could accomplish this?

Thanks!

Nicholas