Just like most other facets of preparedness you need to do what works for your area. What i mean the type of chicken that works for you where you live and for the volume of what you expect to need. One of the biggest problem I see is most people want to go for the hybrid. The Highbred bird can produce either more eggs or more meat, but you cannot do it your self, not really. Producing a hybrid strain is beyond what most people can practically do. You would be better off buying a general breed and work up your own flock. This is a very difficult thing to do and takes time and years of experience. Feeding is another issue that needs to be addressed, if chickens don't get the right feed your egg production will suffer badly. Factoring in predators in your area (which will only get worse, when things turn bad) and learning to deal with them in a different ways (shooting , trapping, snaring baiting) is all part of the process also. Loss from predators must be factored in, excess is another issue either longer term storage vs barter and trading. When you are waiting to increase your flock by setting and hatching eggs is a fairly long process if you have a pressing need.
None of this is magic, in that It happens overnite, but it takes work and years of practice and hands on. Books and stories can only take you so far. One last thought hybrids seldom breed true. What I mean if you buy a hybrid bird (which might be a combination of three breeds already and try to breed it, even to another hybrid, will produce many different thing and seldom what you want.