Don't do a thing until you know the whole plan. Do you want a perfectly dead room, or do you want to optimize the sound of the room itself?

If you deaden the room, then you can add artificial ambience, reverb, etc. If your room is to sound better, then it's a matter of bass traps, and a mixture of sound absorption and baffles to control the natural reflections of the room.

The cheapest short term fix is to deaden all reflections with the blanket trick: Put three hooks in the ceiling to hang two moving blankets or old comforters behind you in a V-shape, the mic facing into the blankets with you singing or playing in between. Works a charm.

But making your room sound good...research and make a well-understood plan before you go out and buy any materials.

http://www.soundclick.com/MarkKaufman