Cooking your own food from the basic ingredients gives you the closest control over what you or your family eat. It allows you to avoid all those additives which are needed to make processed foods palatable.
Vegetables and fruit do not need any elaborate processing. Neither do starchy meals based on rice, potatoes and vegetables. Wheat whole-meal bread from the supermarket is of high quality and can form the basis for up to half your meals.
If your diet does not include traditional pastry or cakes and biscuits it removes the need for a lot of elaborate processing equipment. A food mixer or processor is valuable if you plan to bake your own bread, and a grain mill is very useful for non-wheat flours for special diets.