I noticed they changed "subscribe" to "join" a while ago but I don't think anyone actually calls it that. Is this another change because "subreddit" is definitely the original official term.
I followed specific communities here at first like I did on Reddit, but Lemmy is so small I ended up mostly just browsing the Local feed. It’s a reasonable size (on lemmy.world anyway) and exposes me to some things I would never have found otherwise.
There is also a bunch of crap in there but I find it easy enough to just scroll past what doesn’t interest me.
You should also make a point of checking the sidebars of communities, sometimes they link to a couple other relevant ones you might like. I always do.
If you're a weeb like me, come on down to the ani.social instance. Lots of communities, and again the sidebars of many link to others you might like, even off that instance.
If not, you could consider doing the opposite and blocking the instance in order to cut out a lot of the anime content from your feed, since it's not your deal.
I tend to find stuff by hopping over to ALL now and then, but my sublist is now so big I usually stick to my subscribed feed.
I advice that it gets a lot nicer to scroll through ALL to find stuff, if you don't avoid blocking communities and instances you aren't interested in engaging with. That way the list of content gets shorter and easier to browse in terms of discovery.