Organizing a Minigame Server (Need Tips & Help

So, my last thread wasn't so great, it was just talking about hiring SkyBlock developer. Now I'm willing to learn the fundamentals of java first, then the proper way to host a mini-game server, then I'll be needing tips on how to administrate, moderate, configure, etc. If you could provide me with a good amount of tips/tricks & help that would be impeccably wonderful. I don't plan to for my future network to be popular right away, but I do expect at least 20 people on it or a...​