Fully expose to each individual user exactly how many credits each of their individual items consumes. Add "Credits per month" or some similar attribute to the details section of each item. Allow users to sort their own content by credit consumption.
It's not fair for me to ask my users to moderate their credit usage when there's not enough information available to them to make such basic decisions as, "Is this item worth this many more credits than that item?". Exposing to the user their individual credit budget is not sufficient. They need information that will allow them to make decisions about the relative value of their individual items.
Additional benefit: Many users are afraid to do anything because the credit consumption is so opaque. If you want people to use AGOL, you need to let them know how much it is (and isn't) costing them.