I've run into a problem. I built a room in my friend's house to jam in. We used to be able to play there all the time because his parents have a surverying company and they were usually out most of the time doing surveys. Now that the economy has turned to shit, they have less jobs and I can't jam as much. So I want to sound proof the room as cost-effectively as possible I've looked into Sheet Block and some basic foam squares, but I'm not sure what I'm looking at for the most part. Do I need bass traps, or are they not as important as getting foam on the walls, as the loudest parts of the band are my snare and cymbals. (we're building a drum rise to help cut down drum noise as well) Any tips or advice would be very much appreciated.

You need weight. Anything heavy/dense in the room will help lots. I've found the most cost efficient solution is to use heavy curtains or drapes hung around the room, 2 inches from the walls. Insulate the ceiling if you can with pink insulation or anything dense and with pockets. You could use old book if you needed to in the ceilings. Foam only works if its heavy other wise it woill only diminish the high frequencies, but all the low end will still carry throughout the house.