Help with materials and background

I designed, modeled and animated a transforming sci-fi turret. I was proud, but then I realized it’s just a gray object floating in the void.

I don’t know how to tackle colors or the background. And I want to make something that doesn’t look too basic that would detract from the turret, nor do I want to spend too much time making some elaborate background.

You might take a look at this tutorial…