The number one tip is to search for interesting communities through lemmyverse.net/communities, rather than your home instance’s search. This will let you find communities that are small or new and haven’t been synced to your home instance yet. You can set your home instance with the house icon at the top right, and then all links will open in your instance so you can easily subscribe.
It also lets you search Kbin magazines to subscribe to (through the top right hamburger menu) although federation between Lemmy and Kbin is sometimes a bit patchy.
Other than that, just remember all of the mobile apps are extremely new and if you’re struggling to do something, it might just be because it’s not supported in wefwef yet. Lemmy was clearly built by people who prefer to use desktop, but the mobile website is very functional and gives you full access, so that’s a good place to check if you can’t find how to do something within the app.
Looks like you’ve already got stuck in and been commenting a lot so keep it up, and welcome to Lemmy! 😊