Need Some Advice Concerning One of My Projects

Hi, I need some advice for one of my projects. As you can see in the screenshot below I’m making a 3d emblem. I’ve modeled everything but I’m having trouble setting the stage and mixing colors.
What I want is a solid black backdrop, with this emblem in front and with some mist on the ground. Background will be dark with with some general lighting around the emblem and I want it to be photo realistic. Problem is I have no idea on how to put this type of backdrop up, I can’t figure out at all on how to use the nodes to mix colors and stuff, and I have not idea on how to make mist.
Can you guys please tell me what I need to know to do this and can you recommend some good tutorials? You don’t have to go into detail about each thing that I have to do just want features in Blender I need to know. Any advice would be a huge help.

Thank you!