Subscribe monthly and get a certain amount of credit

Ideally I was hoping to find an app that worked like a photo stock image/Audible/Creative Market type site. Where a customer signs up to a subscription and gets a set amount of store credits to use in my store each month.

I don’t want to have it like a gift card where they spend $10 on the subscription and get $10 credit. I’d need it to have some sort of discount option built in. I.e. They subscribe and pay $10 per month, but get $15 worth of credit to spend in the store. Or, there’s a 25% discount somehow built in when they spend in the store.

I’d need it to have some sort of automated workflow, so that once it’s set up, it runs with minimal intervention from me. Potentially integrate with Kit (formally ConvertKit) for any automated emails I need to set up.