D.I.Y. Isolation booth help (budget)

How's it going everybody? We're building an isolation booth (we had originally budgeting some to let a professional do it - but after buying equipment, credit card bills, etc.. this is fiscally impossible, and we must do it ourselves) - i know this effort right now is kind of rudimentary and cave-men like.. but what're we gonna do.. The Project: 8' x 8' x 7' 1/2 room we have built a basic boxing frame, and now need help sound proofing it... we have this basic frame up and two walls, and we already have run into problems with a creak in the floor -- I was hoping to get something in the floor, but they built it today while i was at work and just left the floor hollow... this is just a very basic frame right now we were planning on insulating the walls anyway possible and then side it with 1" MDF Boards and then line the boards with sound foam... we are running on a very low budget, i know everyone here is an expert, so what are better ways to soundproof it...?