Podium at Dakar? No problem.
The answer to the gravel road is the same answer I give to most questions which revolves around the basic fundamentals of riding. First is that most riders ride out of balance (at least slightly) a majority of the time. And when you are out of balance the effects are amplified if the traction is compromised (gravel, sand, mud, snow). Second is that most riders compensate for the balance issue with speed or momentum. Add the fact that you are uncertain about the surface you are riding on and being tense or tight on the bike compounds the problems that are occurring. So in reality what is happening is a series of corrections, none of which are actually helping you to ride more relaxed, more in control and more efficiently. A lot of times you feel that you are not going fast enough (more speed would make you feel more balanced) and at the same time you don't feel comfortable slowing down (the out of balance shows its ugly head.)
OK, so in reality what we teach is recognizing a high level of balance and to have excellent control of the motorcycle through the throttle, clutch and brakes and using your balanced weight to control the bike and make it go where you want it to. Riding like this you rethink the braking points and then the lines you take when riding. You'll feel like you are going slower but in reality you'll be riding faster, mostly because of the far fewer mistakes that you make. And all this takes is practice once you get pointed in the right direction. It takes a full day of drills to put all the pieces together but after that it is all about practice and you can do that any time you are riding the motorcycle. Being in better control of the brakes and throttle only amplify the control you have on any surface.
As for the proper bike, the smaller the bike the more you will learn in the class as you can take the drills and push them farther without getting uncomfortable. Though we teach the same skill sets no matter the type pf bike in the beginning.
If you are riding out we have some smaller rental bikes you could use.