There are plenty of such champions on Ubi and ToH. In my first tournament three years ago, I saw IRMG+ templates for the first time and immediately played against some strong players; that's where I learned. Now it's much easier; there are excellent streamers, and they are a treasure trove of experience.
In my opinion, it's necessary to create a tournament with two groups of players. While the games are being played in the groups, players will have a chance to learn the basics and understand if they even want to continue. Some will drop out, and the best players will move on. But they must play against strong opponents; otherwise, there is no point in such tournament experience.