First, welcome to PBF.
First and a half: Congratulations on building your new pond. It will be a lot of fun and frustration. The good kind, if there is such a thing.
Second, it would benefit you to do a lot of reading in the structure archives. It will answer a lot of questions about what to put in your new pond including the question you just ask.
structure archives Do you need to add gravel? LMB and BG will spawn profusely without it on a mud bottom. Will the fish utilize it and be beneficial for them? Probably. Depends on how much work and expense you want to go to to set up the best possible situation for your fish.
My opinion answers. I'm not an expert. The experts will be along shortly with correct answers.
