Page Data source

Hi , I have recently created a custom filter which comprises of two drop downs. I have set both drop downs to Auto post back and have used logic in the code behind to create dependencies between them. The first filter displays categories, and the second displays child categories, based on the selection. This seems to be working fine. On my page i have added a , Page Data Source and a Basic repeater. I am struggling in how i need to set up my data source and repeater, as i have been following the product custom filter tutorial. Basically i want to filter documents based on the root or child category chosen. Are their any default data sources and transformations which would get me started on this issue ?

Regards