I don't like "big" instances, since they tend to quickly walk back on their promised goals once they no longer can manage their size. So when I joined Lemmy it was on a smaller now defunct vlemmy.net instance. The idea of operating and moderating the community was not that appealing, but it was a way to promote the instance, so I started !globalnews@vlemmy.net and !databreaches@vlemmy.net. It was a slow start, but they grew over time, reaching 1000/400 subscribers respectively and then the admin killed the instance and vanished. That was a lesson.
After that, I joined lemmy.zip, it was tiny then, but it had a lot of things going for it, multiple admins, multiple communication channels, transparent finances and good base rules. What it lacked was content. So I had to decide if it was worth my time to start over by creating another community and help it grow. I re-started !globalnews@lemmy.zip and !databreaches@lemmy.zip and just started posting without any expectations. It was an outlet to share what I found interesting or what caught my eye. Eventually, people started commenting, and organic discussions started happening. I expanded the number of communities I moderate now, but the principles are the same. No expectations.
So the reason for all this backstory is that I stay motived by believing in the project and wanting to help good instances to grow. If not for Lemmy I wouldn't be posting anywhere else, never moderated on Reddit, never even posted on Reddit, was a habitual lurker there.
Just find topics you are interested in, maybe set up an RSS client and share the content that you find interesting yourself.