This probably won't work for everyone, but whenever I'm learning or trying out something new and unfamiliar, I always tend to follow the philosophy of "Just jump straight into the deep end and you have no choice but to swim".

So for those thinking of trying out Lemmy/Fediverse. I suggest trying to get your own instance running. It'll get you more familiar with what Lemmy is and how it works (at least on a high level). Its also really rewarding when you get it all up and running, it becomes something more personal to you since you took the time and effort (instead of just clicking sign up on some instance).

But again, that just how I prefer doing things. To each their own.

wefwef.app is a great alternative for those who are used to Apollo.

Don't join the biggest instance.

I use this userscript with Tampermonkey for a layout that's closer to old.reddit. (Script not mine.)

Once you understand that federation is a process managed by each instance it is easier to navigate communities

Your account is on an instance (server) that will only see communities on other instances if someone on your instance has already subscribed to that community

If you joined a large instance you might already see a lot of communities in your feed that you can subscribe to, but you might be missing some that exist but won't show up in the search

A solution is to use lemmyverse.net or a similar site. You set your home instance, then search for communities. It gives you links that open on your instance where you can subscribe to (or block) communities. You do this in a browser, and it immediately reflects in the apps

e: If you are coming from reddit and just want to know what communities align with a particular subreddit, you can use sub.rehab then search for the community on lemmyverse