Us early adopters have some advantage in that we have grown with the communities. You’re now looking at a much larger list than we did.
I would search for stuff you’re interested in and subscribe to them. Then maybe look at the mods and see what else they have posted and commented on. These will likely be people that are engaged well on lemmy and may have similar interests as you. Maybe subscribe to places they are engaging with.
After you have a solid base of 20-40 communities, use the All feed and sort by newest posts to try and find stuff you may be interested in and are active. That will show stuff from lots of other instances.