I would like to know how to build the code or if there is script I can use to be able to credit peoples accounts with credits if they purchase the credits.

Like if you pay $1, then you get one credit that can be used to buy things.
If you pay $5 then you get 6 credits.

Then with the credits I would like the people to be able to buy items with them.

The main reasons for credits is to make my site look better / professional, and for where people can get additional credits like if they buy certian ammounts.

Thanks in advance! :)