Since you got boosters you really could set up your track any way you want. I don't know how much room you have or how wide of a lane you guys need but I say 3 sets is a safe bet. What's gonna happen is that you'll have more than enough curved pieces and run out of straights the bigger your track gets. My first track was 6x 12 feet and I used 4 sets. I'm now restricted to a 6x6 track and did well with only 3 sets. I think Rs needs to start selling individual pieces.
