that's exciting!
I don't know how extensive you want to get at any point.
Maybe get some good soil for the top third and grow some lettuce or brassica starts from a store. Or spinach or mustard or kale seed.
I could see starting a compost now. Can you get a lot of tree leaves this autumn? You could be layering fall tree leaves with the dirt as you go. It will settle a lot as it composts. Kitchen scraps can go in also.
there should be more suggestions coming..
