Yes money is always an issue, some people have it some dont. Its just something we all have to work with.

So without further adue, try painting the inside of your grow shed white or cover the walls in mylar. I would stick with paint in your case because it's cheaper and reflects almost as well.

I also suggest either purchasing a sliding rail for your light ballast or building one. There's many things you can do with minimum ammount of things to improove your room, you just need to be artistic