I recently started keeping a few hens and want to make sure I am not giving them the wrong food. There is so much conflicting advice online about grains, kitchen scraps, treats, and complete feed that I am not sure what should actually make up the main part of their diet. I would rather get the basics right from the beginning than correct nutritional problems later.

What would you recommend I feed my chickens on a daily basis, and how much room should I leave for treats or scraps?

For the main diet, I would rely on a complete poultry ration that is formulated for the birds’ age and stage of production rather than trying to mix everything myself.
Chickens should receive a balanced prepared feed containing the necessary vitamins, minerals, and protein, with laying hens also needing adequate calcium and grit.
A helpful American overview on how to feed chicken also notes that fruits, vegetables, grains, and insects can be part of what chickens eat.
I would treat kitchen scraps and scratch grains as extras instead of letting them replace the nutritionally balanced feed.

A complete ration should also match the bird’s age and production stage.
It makes sense to distinguish between starter, grower, and layer diets, especially if the flock contains birds of different ages.