There are a lot of different ways to train, and different thoughts on gear too, so it's going to depend.
I started with a Comfort Flex harness like the one Lauren pictured, but my club doesn't like harnesses and I got a lot of pressure to stop using it, so eventually I did. I needed something to grab ahold of though, and Halo is a coatie and a regular flat collar got lost in her fur, so I bought a special flyball collar with a handle on it. Since you're just starting out I wouldn't worry too much about buying anything special unless the trainer encourages you to do so.
We use a target stick to train the box turn, so targeting is one of the basic skills we start with. Other people prefer to lure dogs onto the box, and I'm sure there are other methods I'm not aware of. But it's a good skill to have, so you might want to start working on it just in case. I taught Halo a hand target (nose to my palm) starting when she was just a puppy, so it was easy to transfer that to the end of a target stick.
Tugging is good too, although he'd rather work for food you can use that instead but tug is preferred. The kind that most people use is long, so it will drag on the ground as you run away. Braided fleece is very popular, but may not hold up to a GSD for long. Tugs made from climbing rope are good too, or with climbing rope braided in with the fleece to add strength. I ended up making a special braided fleece tug for Halo that has Orbee balls on it because she wouldn't drop the tennis ball for the tug.
If he will already retrieve a ball, that's great. If he'll retrieve a ball for a tug reward, even better! A balance of ball and tug is best because you want them driving hard in both directions - to the box for the ball and then to hold onto the ball all the way to you for the reward. If he does retrieve but doesn't have a strong out, work on that. If he'll retrieve a ball but drop it before he gets to you, work on having him bring it all the way to your hand before dropping it.
The very first thing we do is determine which way the dog turns naturally. We do a "dead ball" retrieve, where the owner restrains the dog and tosses a ball a few feet away. It doesn't have to be far. Wait for the ball to stop rolling and go "dead", then send him. If you do this 5 or 6 times and he always turns either to the left or the right every single time, that's his natural turning side and that's what you're going to train with. Some dogs don't seem to have a preference, our club is teaching classes right now, and I got TWO dogs that seemed to be ambidextrous! One right turn, two lefts, two rights, and a left. Gack! You can also observe which way he turns when he goes into his crate. With Halo I was pretty much 100% sure she'd be a righty before we did the dead ball retrieves in her class because when I go to put her food bowl on the floor she spins in a circle, and ALWAYS to the right.
As in Lauren's class you'll probably be doing lots of restrained recalls, which is basically the end of a flyball run. We start out on the flat (no jumps), then start backchaining the jumps - one jump recall, two jumps, then three jumps, etc. We put gates at the side of the jumps to encourage the dogs not to run around them. If you have a friend who can work with you on restrained recalls, that's something else you can do in the meantime.
That's really all the foundation stuff I can think of that you can do on your own. For a lot of things you not only need to know what you're doing but you also need extra people and equipment.