Would definitely put the shed on some sort of platform, be it concrete or wood floor. We have used 4by posts in concrete with joists bolted to it to make sure it is level. After that, we build the floor system and anchor the system with 4by's in concrete as well. Then we build the shed. I personally like the one called Arrow at Lowe's. Good shed, somewhat easy to assemble, can anchor to the wood floor, simple and easy. Usually takes us about 2-3 days. Get everything squared up, plumb and level. Have built many. Have one in EAV to look at if need be.
Ron