First thing is consider the enviorment. If it's a basement with sheetrock your sound is not going to be absorbed by anything. Carpet is not enough being just on the floor.
I don't know your age or if this is something possible. The reason i'm saying this is, if it's your parents house, they may not want you putting things on the walls.

If it's your house, something like "Honney!! OMG! The dog ran outside!!" and then she forgets what you're doing.
Assuming low amount of resources first...
Blankets (thicker the better) and allow some distance from the wall (a foot or two). Build a rack for the blanket in the shape of an L and then you can easily move them around the room until you get the room as dead as possible.
Another thing to consider is EQ. I had an old Fostex X-4 (I believe that was the number) many years ago. I recorded direct from
an ART SGX2000 and
Peavey DPM2 SE, but in the mixdown, I ran into an EQ and trimmed off the 12khz range and removed the tape hiss. Came out MUCH better. May want to try that on your recording and see if you can kill off some of the background noise. Just try some of the different EQ settings. Correctly set, this should help in the overall sound of the recording.
If this is going to be a permanent studio. Then you would be looking at going into more details and considerations. Contact me if this is the case and I will be happy to point you in a good direction there.
[--edit--]
How are you recording the instruments? Are you recording them all with mics or running everyone into the board? You wouldn't have to worry about accoustics (and get a cleaner sound that you can work with MUCH better) if you ran everyone direct into the board.