I can't really offer much advice. When you say "self sustaining", do you mean you want a flock which can take care of themselves, in that you ideally don't want to provide feed for them? Or, are you referring more to the subject of reproduction. If it's the latter, then I well and truly can't help as I know very little about breeds. If on the other hand you want a free ranging flock which requires little or no feed, then you need to look into what birds are best suited to that way of life, as I would imagine certain breeds are simply no longer capable of providing for themselves.
I' as you can see, live in Thailand, and I started my flock with a few birds which were given to me by one of the locals. These are native Thai chickens (game birds) which one finds everywhere over here. Most Thais simply allow the birds to run wild and breed as they wish, but because not all people have one of the larger Thai fighting cocks to breed in a good size, many of the birds are quite small. With that said, these birds are 100% self supporting. I myself have recently allowed my to free range from dawn to dusk, and after just two weeks, they are no longer interested in commercial food at all. Hopefully my two ducks will eat most of what's left before I have to throw it all away because the chickens don't go near it anymore. I still get beautiful eggs, and I have a flock which is happy and content. The bug population is down, including the ticks, and the coop/run smells a whole lot better as they're only in there to sleep. Most of the hens also go into the coop during the day when it's time to lay an egg. I want decent sized birds, so as I go along, the small ones will end up in the freezer, while the larger ones will be kept for eggs and breeding. All roosters will be processed before they start doing their business, and chick making will be left to a lone fighting cock.
On the downside, some people don't favor the meat of these birds because it's not as tender as the chicken you buy in the grocery stores. I prefer the taste of our chickens and so does my family, and I would imagine many others on here feel the same way. Just one month ago, I was determined to get in a few different breeds, but now I've changed my mind, because I didn't start with chickens in order to have several breeds. I started because I wanted to raise our own meat and eggs, and by meat, I don't meat broilers. Each to his own, but if you ask me, when you eat commercially raised chicken, or even self raised broilers, you're really just eating recycled chicken feed. When I eat one of our birds, I'm eating recycled grass, weeds, and bugs.......just as nature intended. And, when I eat some of our eggs, I'm no longer eating recycled layers pellets. I know not everyone can free range, but if you can, then it's the way to go, and if you can cut out commercial altogether, then that's even better.
Just the other day I asked a friend if they've ever tasted what a free range egg tastes like, and he replied "yes", him and his wife only ever buy free range eggs when they go shopping. I don't know about the states, but for he most part, you cannot get "real" free range eggs in a supermarket.
Anyway, sorry for the long post, but just wanted to share