Start out by getting a commercial feed and read the tag. Most feeds will vary on what ingredients are used due to what is available to the feed mill. Most of the commercial mixes are corn and some other grain and grain by products with the necessary minerals and vitamins added. As to the foods you can feed them that is, again what is available. Chickens are omnivores that can and do eat just about anything. They can eat just about anything you can. They need around sixteen percent protein so if they are getting a lot of low protein greens they need to make the protein up with bugs, worms and other meats or something like soybeans. Starting out I would stay with a commercial feed as the basic and supplement that with other things.