In Vegetarian literature, it is suggested that corn with beans produces a complete protein. I don't get the science behind that, but the Inca and Mayans lived off that for hundreds of years. Good thing chickens can eat worms and grubs, too.
It has to do with amino acid complimentation. Plant-based proteins are incomplete - they often have low (or effectively no) levels of certain critical amino acids making up their proteins. For purposes of chicken keeping, the four most inmportant, in order, are Methionine, Lysine, Threonine, Tryptophan.
In general, Methionine is hard to find adequate amounts. PERIOD. Its also the most important AA, particularly for hatchlings. A chicken's need for it declines as they age. Per pound, your best sources come from legumes and dried legume forage (soybeans, soybean meals, cottonseed meal, peanut meal), plus sesame seed, tef, hemp seed, and white "proso" millet. Italian "green" millet, amaranth, fenugreek and gram are all average sources. Won't boost your Met levels vs target, but won't hurt them, either. many of those sources are very high fat, so their use needs to be limited.
Lysine is next most important. Once again, soy and soy meal do very well here (its about as close as you will get to a complete and balanced plant protein). Cottonseed and peanut meals. Then come all the beans (ever wondered about rice and beans? This is the bean's contribution). Faba beans, cowpeas, lentils, winter peas, gram and fenugreek slip in there, then chickpeas. Most of these need heat treatment to correct some antinutrituve properties, and some need to be kept to small portions of the chicken's diet for other reasons as well - usually the presence of tannins, beta glucans, tryptosin inhibitors.
Threonine is next - and the list looks much like the Lysine list, beginning, once more with soy meal then descending thru the beans.
Finally, Tryptophan. Yeah, there's that soy meal again. As it turns out, birds don't need a lot of tryptophan, and its almost impossible to make a diet low in the stuff in the typical wheat-based or corn and soy based diet.
Regarding millets, in general, the darker the millet, the less nutritious it is for your birds - not only on the basis of chemical assays, but also due to increasing tannin levels, which can interfere with absorption of nutrients.
As to the beans, in general, cowpeas (black eyed peas, etc) are superior to faba are superior to lentils are superior to winter peas are superior to chickpeas - but the last two reverse with regard Lysine and Threonine.
Since all this stuff is complicated, and involves delicate balancing, I strongly recommend avoiding monolithic plantings of a single crop or two, which can easily imbalance a diet, and instead placing a large number of scattered plantings from multiple categories - I have four varieties of clover growing, for instance - each comes into seed at a slightly different time. I've planted amaranth, sorghum, buckwheat, millets. Have a number of herbs - fenugreek, yes, but also thyme, oregano, trying to get some mint to take hold. Planitng peanut this year, if I can find some. None of the peas have done well for me, will make more effort at those next year.
Then let the chickens forage.