Alright mate, first things first you need to ask yourself if you have the work for 3/4/5 ferrets as opposed to 2. If so then crack on.
Same with breeding, you need to ask yourself do you REALLY need more ferrets, and if so, do you REALLY need to breed a litter yourself, of potentially 10 + kits, if there are other decent litters available to you to have kits from.
Sounds like you are on the right track with regard to getting in a young jill and working her before you breed, but it will take a few good seasons to figure that out. FOr example, kits born this summer, will not really work