There really isn't a perfect diet. All chicken people feed a little differently than others. Some might only rely on commercial feeds, some night mix their own formula for feed, some might feed greens and veggies and meats with the commercial feeds being an add in and not the main meal.
For a new chicken owner I suggest - Give them a good well balanced commercial feed. Starter or starter/grower in the beginning. When they reach the point of lay change them over to a layer feed. Keep feed, oyster shells, grit and fresh water available at all times.
For treats black oil sunflower seeds, mixed whole grains, oats (like oatmeal), yogurt, rice, chopped boiled eggs (with the shells) or however you choose to cook them, etc. Even table scraps is okay for them.
Some people refuse to give their chickens meat or meat scraps but chickens do eat meat. They love bugs and worms and insects. They will catch and eat lizzard and frogs and mice, among other things. I give my chickens meat scraps from my kitchen, as well. I often will buy crickets or meal worms and give those as a treat too.
A wide a varied diet produces eggs with deep orange yolks and high omega 3 fatty acids.
Good stuff.