Rule #1: reblog, reblog, REBLOG!! Tumblr doesn't have an algorithm like Twitter or Instagram or Tiktok. Reblogging is the only way to help share artwork or memes, and you can add little notes in the tags! If you wanna help out artists and fanartists, make sure to reblog things if you like them :)
Rule #2: Customize your blog ASAP!! There's a huge bot problem on Tumblr, so adding a pfp, header, and intro is IMPERATIVE if you don't wanna be blocked. Oh, also, if there's a blank blog following you, block it. It's most likely a bot.
Rule #3: don't like, don't look. If someone ships something you don't like, has a take you don't agree with, or maybe just is a lil too annoying- scroll past. Block them. Block tags (I can show you how to do this if you are unfamiliar.) tailor your Tumblr experience to YOU! Don't worry about other people. Just be kind and do what makes you happy :)
I can link some good videos that will explain the mechanics of Tumblr and stuff, but I'm in class rn and our control freak teacher is super strict about phones, so I might not respond for a while. Good luck! π