As stated above, free ranging provides the healthiest and cheapest supplement to your feeding ration. You might also find that keeping a continuous feeder may also be feeding the local rodents....you'd be surprised how much they can carry off and store for their families.
I free ranged at all times. I bought 50-100 # bags of whole grains like wheat, oats, barley, cracked corn, sunflower seeds, oyster shell and laying mash. I mixed my ration equally and fed once a day....evening feeding in the warmer months and morning for colder. I used a trough style feeder with welded wire over the trough to prevent scratching and flicking. I only put out as much as the chickens can eat at one time with only a little left over for a second small feeding/snack.
Also as stated, supplementing with garden produce or salad trimmings, family leftovers, etc. will also fill bellies.
The whole grains seemed to fill them up on less amounts than just laying mash. The whole grains won't mold as easily when stored in large amounts. Cull any birds that are not needed or not producing, not fulfilling your flock's desired traits/genetics or just causing trouble in general. Too many good, productive chickens out there to feed free-loaders, problem children, or weaklings.
Remember.....chickens won't be cheap if you think with your heart and you can't save money on sympathy.