Dude go with the closet in your room. Its pleanty big enough for 3 plants. I wouldn't worry about covering the walls with mylar, the room is already painted white so thats fine. You could use mylar if you have the extra cash of course. I'm not sure if the light in the first picture is the one you're using or not but if it is, you need a reflector on it so the rays aren't wasted and get focused on your plants.