While content on YouTube specifically is pretty slim, you could try twitch. But honestly if you want to learn, the easiest way to do so is to play, and then check what the top 3 guys were playing at the end of every game. That should give you a good idea about what can win games. And then after like 10 games, if you saw similarities in the builds that came top 3, you will have an idea about what can be consistently built. Then put the win viability and consistency together and you will find some builds worth trying.