Couple tips:

• Don't overthink the whole second brain idea. Just take notes whenever you need to take notes in whatever format works for you.
• Don't overdo the thing with Plugins, only install it when you really need it and remove plugins when you don't actually use them.
• When you get a lot of notes, then it's good to do a bit more structure that works well for you and you can even start automating some stuff in Obsidian.
• Learn the keyboard shortcuts well and modify them to your liking (here are my favorite Obsidian keyboard shortcuts).