Not just you!
Seems to be hitting all the hot button topics. Protection training, breeding, fearful dog, dog food debate...
In short, many of the things a newbie might be interested in until they know more.
To the OP, do not be in such a hurry to breed or make this decision.
If your dog starts normal cycling, than she should come into heat at 21 months. That is good, not bad. Do not breed her on that heat. Wait three months more, 2 years, and take her to a vet known to do good x-rays.
Have them take x-rays and send them in to OFA for hips and elbows -- you want to know whether you are breeding or not. At this point she will be in the middle of her cycle and not loosened up due to her heat, etc.
Also check for Von Wilbrand's disease -- blood test, OFA thyroid and Cardiac, and while they are at it, have them CERF test her -- for the eyes.
In the mean time:
1. Join a GSD club, with real live people, hopefully some with working lines and some with show lines. Get to know them and their dogs.
2. Get into training, join a club, take her to classes, take her to shows, get her titled.
3. Research your girl's pedigree, get to know the various lines. Get to know what the dogs in her lines were like. Get to know about any accomplishments of any of these dogs.
4. Get books about the German Shepherd and read them, read books on genetics, training, nutrition, and breeding. Learn all the different things GSDs are prone to healthwise -- hip dysplasia is not the worst thing out there, but it is best known. Everyone asks about it. And what you need to do is be an expert and answer questions about all of these topics, if you want to breed dogs. Learn about what might go wrong during whelping too, the signs that everything is not right, when to go in and get an emergency c-section.
5. Find yourself a breeder -- does not have to be GSDs, but someone doing things right. Someone who shows and/or titles her dogs, someone who has plenty of experience, someone who is a member a breed specific club or training club, someone who does the appropriate health tests for her breed. Get to know this person and try to gain from her experience in whelping and raising litters. If at all possible, be present -- unlikely. Or, help to socialize the puppies after they are born.
Your girl is YOUNG, you have plenty of time to do this right. In my opinion you will still be a back yard breeder, because breeding once and then spaying, in my opinion, is not breeding toward an overall goal. If everyone bred their female just one time, we would be way overrun with with dogs in just a few years (though many people think we are there already). Reputable breeders breed to maintain the breed, they pick dogs that best match their bitches, they breed to hold back one or more and breed again, they health test, and they prove their dogs' temperament, they spend time and money on the endeavor and rarely realize any monetary gain, they put their lives into it not just their spare change and spare time.
The biggest thing is finding good homes for the puppies. Believe me, family and friends run for the hills once the puppies reach eight weeks old, people that said they wanted one, suddenly forget you exist. And while you can always get rid of them cheap through the newspaper, you will have to do a lot of time and energy to ensure that the pups are going to good, responsible homes.
Do not think that she will have two or three puppies and you will keep them all if necessary. She can have 12-14 puppies and you will up to your eyeballs in smelly newspapers and literally poop in no-time.
Good luck. The breed needs new blood, but only if they are committed to the breed and to the dogs they produce. There is a lot to learn and a lot to do, I have only chipped off the tip of the iceburg.