Ideally I want users to earn "credits". These credits will allow them to redeem "content" (nodes). My goal is basically to allow users to only gain access to content they "redeem" using their credits, and they only gain credits by submitting content which I approve and assign value to. So if user X submits content, I think its great and rank it 8 out of 10 and decide that he gets 8 credits, he then gets 8 credits. He can then use those 8 credits to redeem content, and content can have different values.
What is the best way to go about getting this functionality in Drupal?