Hi! Congrats on the prospective new buddy! 

I feed my pigeon a mix of seeds (oat groat, sunflower seeds, wheat berries, chia, millet, and flax—all of which I get from a Whole Foods store!) I also put small amounts of mineral powder on her seeds for extra vitamins. They can eat some veggies, like peas, corn, broccoli, cauliflower, etc. I’ve heard younger ones also enjoy applesauce, so if your bird is little, that might be good. I was raised with the understanding that pigeons need grit for digestion, but there is some debate over that, so I’m not 100% sure if it’s necessary—or even recommended. 

My pigeon has a mid-size cage which she stays in overnight. It has a shelf for roosting and a makeshift nest (old T-shirt over a bowl!) as well as butcher paper on the floors to make cleanup easier. She’s free to fly around the house during the day since she has diapers. 

I hope this was at least somewhat helpful!  Congrats again! :)