Credit system can be consider as a e-wallet, which this system user can

• Earn credit thru doing activity like adding friend, comment on a post, share a post…..As admin, you can control which actions that member can do to earn money.
• Send credit to friends or buy credits from admin
• Use credit to pay for membership as a normal payment gateway
• View full transaction history/log

As admin you can

• Send credits to any user or many users
• Create credit package for user to buy
• Define exchange rate for the credit. Ex: 1 USD = 1 credit