I used 96" White Pine 2"x4" Studs. $1.96 a stud, but went through 50 of them to find actual straight studs at Lowes.
1/2" 4'x8' chipboard. Talk with a lumber guy, Lowes will sell you a sheet with a chipped corner really cheap.
3" and 1 1/4" screws
12'x8' sheet of indoor/outdoor carpet. This was about $45 at Lowes. I know they make synthetic putting carpet, but I think the ball rolls really good on the carpet if you stretch it really good right after gluing...