Many shooters just shoot for the sheer joy of seeing those little clay targets explode into balls of orange and black smoke. There are all classes of shooters, from novice to professional. Certainly, a registered shoot is not a good place to learn how to fire your first round of trap. But they do have practice traps and after just a few sessions you should be ready to begin shooting the tournaments. Go to a gun club before the registered shoot, get your initial lesson so you can learn the procedure and etiquette, then go to the big shoots.
Every gun club has members selling shotguns.
You don't want to spend a fortune on your first gun because you don't know what you need. You can spend a few hundred dollars for a good used gun, as low as a couple hundred or less for a starter trap gun, or a few thousand for the elite guns. It's not the gun, it's the shooter who wins. Many shooters shoot old outdated guns and win shoot after shoot after shoot leaving many with the expensive guns behind in the dust. The investment is low.