Here are some ideas of what to do for room treatment. These techniques are for tailoring the acoustics of your room for recording and mixing music. They do not substitute for sound proofing. However they will help to tighten and isolate the sound source for clarity and tone.
If your problem is sound coming through the walls then some other things would need to be done as well. but as you are mainly just doing vocals building a vocal booth that can be broken down is not very difficult.
building wall panels and bass traps.
the basic room placements are like this. for this i would be mixing in the long field of the rooms direction. I think that is what I gathered from the pictures.
you can use the Panels to build a vocal booth like so...
and staple velcro on to them so you can velcro them together like this
I you wanted to go further the next step would be panels on the ceiling AKA sound clouds...
Same basic construction as the panels but 4'x4' depending on the room size that might change. You want to run cross members like in the bass traps. 16" on center.
When I do my thread I will post details on slat diffusion panels and corner trapping as well.
if you have questions as to how many it all depends on room size. There is a ton of info in the Tips and techniques section for how to figure that out.
I often have people who want to enhance their door. Building a panel big enough to fit on the back of the door helps considerably. just remember to leave a notch for the handle.
Building them yourself can save you thousands... trust me.