Translating points earned in a Q&A forum in to credits in a digital wallet

I have created a e-commerce website in wordpress and i intend to create a Question and Answer discussion forum as an addition to it.

The main functionality is to translate the upvotes/likes in to credits with which the users can buy stuff in the ecommerce website. Both the ecommerce site and forum must have single login.

What is the best way to achieve this? Which plugins I should use.

I am a newbie, so nevermind if this question is too amateurish Thanks

via Chebli Mohamed