I recently bought a new 80x80cm light cube.
Before I tried different sizes, but 150x150cm was too big for my room and 60x60cm - too small for most of objects I planned to shoot. 80x80 is perfect size!
I also tried to build light cubes from tripods and paper, but the construction wasn't too stable, occupied much space and took forever to be removed and placed back. The real light cube can be folded and unfolded in seconds - another advantage.
I'm so happy now! Isolation is no more a problem, because the cube makes the background lighting so soft that all it's structure disappears, after which I easily get rid of it with a couple of magic wand clicks.
Also the walls of light cube help to fight useless reflections of room furniture on shining surfaces :)
So, I would say this is one of the best pieces of equipment which photographer can buy just for about 50-70$ (mine is from Raylab and cost me 65$ including delivery).
Here are some examples of what I've done with my new toy.