I know of a few hatcheries in various parts of the country, but I don't know of any breeders that aren't hatcheries. (They almost certainly exist, I just don't know of them.)
That sounds like a good plan.
If you keep notes on things like weights at various ages, you will have the information to compare if you try any crosses, to see if the crossing is making things better or worse.
If you want to raise purebreds, look for the traits that are correct for the breed. But if you are wanting to make mixes rather than purebreds, look for the traits you want to add to your chickens. You may even prefer traits that are "wrong" for the breed in question (I know of someone that was...