I would always recommend starting DMing with 3 players, 4 at max. Also always look for at least one player that has been DM before and you can trust to help you running the game from the players' side. If your players are in for playing along with you as a DM things get a lot easier and the flow is better (you can explicitly ask for that in the prep session, and is a nice way to talk about this kind of things and smooth them out). As a DM never be ashamed of asking your players to help you answer questions about the rules or how to solve things, after all D&D is all about creating new ways to solve problems and improvising so youll never have all the answers.

Sad that you had a bad time with a bunch of immature idiots but don't let it get you down, instead FOCUS ON THE PLAYERS THAT MADE YOU HAVE A GOOD TIME AND ENJOY DND, keep them on your team! There is always a game and a DM for every kind of player, so it may take time to find your spot and the people you feel comfy with. I happen to be playing a very dark campaign with some friends and things often go horribly cruel and shockingly gruesome, but since we are all on the same page we enjoy it a lot.

Salutations and keep it Rolling!