It probably depends on the breed.
With GSDs being very popular and having many different lines and types, yet being a very young breed with a lot of linebreeding, it's very important to really know lines, pedigrees, what dogs improve what or throw what problems. There's a TON of linebreeding in some lines so you really need to know a lot about what you are breeding, farther back than just 3-4 generations because at least in the Am line and west German show lines, a huge majority of the dogs go back to a dozen or so. I've thrown myself into this breed for about 3 years now and am *just* now getting to the point where I can look at some dogs and predict their lines/parentage and that sort of thing.
I have found that just through the process of training, titling, joining the clubs and breed orgs, and being out at GSD shows once or twice a month, I keep changing and refining what it is I personally like and don't like, what I'd be looking for if I were breeding, etc. I'm not interested in breeding but if I were, I'd wait until I had a very clear, specific goal for my breeding program. Set yourself apart from everyone else with your breed, give them a good reason to choose your dog over all the others.
I'm actually in your position now because I'd rather own males and I'd rather be more involved in training, showing, and titling than breeding and whelping. Also I think kennel-blindness is a HUGE issue in GSDs right now and it's really turned me off to breeding. People ask me if Nikon's a stud dog and I laugh because he's a puppy! Maybe he will be, maybe not. It's impossible to tell right now. I would not breed him ever unless he met all of *my* own criteria. Also, financially I can't do it right now, no way. When we bought our van the salesman kept apologizing for all the paperwork and I just laughed and said you think this is a lot of paperwork, try registering a dog conceived in a foreign country! Nikon alone has 4 registries (AKC, UKC, WDA, USA/SV), tattoo and microchip certification, USA and WDA scorebook, AKC DNA, Avid microchip registration...on and on...plus the paperwork for every show, title, and event. My tax files pale in comparison to my dogs' paperwork! After all that, plus the money into training, proper care, proper nutrition, transportation to events (this is a HUGE one for me, way more expensive than the events themselves), show entries, titles, etc. I can't afford to do all this for more dogs for a kennel, plus the costs with whelping and raising pups. My mind is spinning just thinking about it! Good breeders are selfless! *bows*