Pesonally- My chickens get any leftovers from the night before, or whatever is about to go bad in the fridge (notice I said about to go bad- not bad already). I also, no longer put the compost in a bin....I throw it in the garden area and they pick through it. One source of extra greens is to ask your local grocery store for the Wilted/bruised greens/fruit and tell them its for your chickens. They will often give it to you for free and then it's nice to give the person a few eggs later. Some of it is often also good enough for us humans to eat---so that's a bonus (don't tell them though!)
I've heard RAW potato peels are bad and too many onions can give an oniony flavor to the eggs (although that might be ok for an omelet!). Hot peppers do not affect birds like humans, and actually have good properties for chickens, so go ahead and give that to them. Giving them a handful of sunflower seeds (like the kind for songbirds) can be really good for both egglaying and feather condition. Chicken scratch or cracked corn is an ok treat IN MODERATION. Corn is often given in the evening during cold weather as it takes extra energy to digest and thus "gives off heat".
On another get it cheaper note....I get wood shavings from a local cabinet maker. I have to pick through parts of it sometimes and get stuff out, but it's FREE. ALso, Pallets (especially from hot tub or 4wheeler dealerships) usually have good wood on them that will a little effort can be used to build coops, nest boxes, etc. My nest boxes are dog cookie boxes from the feed store I got for free---I just put them on their side, took 3 of the 4 top "flaps" off, and taped closed the last flap to create a lip that holds the bedding (and eggs) inside. I have two of these stacked inside the coop.
You also might check if you have a local freecycle goup (freecylce.org). Here you can list what you want or what you might have to offer and everything has to be free.
Good Luck and Enjoy your chickens!
Sandra