Pouring a concrete slab in old basement

Hello, I'm looking for some advice on a project I'd like to undertake in the spring/early summer this coming year. I bought an 1860's farm house, post and beam on a field stone foundation. The main section of the house has a full basement, and the later addition has a crawl space. The full basement currently has a few inches of crushed gravel on top of clay(fitting as I live on Clay st.) It is moist down there. This winter I am re-pointing the foundation and then painting it with drylock or comparable sealing paint. My goal after that is to have a concrete floor poured in. I'm planning on 4" of cement, but I'm not sure if I should remove the gravel, and pack the ground, and how I should build in a drainage system. I would think I would want some type of collecting troth around the perimeter to a sump-pump, but I don't know what products are out there, or if this would be the proper thing to do. Any advice for this project would be great! Also, this sub-forum is the only place that seemed appropriate to place this question, if it should be moved else where please do.