Some advice I have seen (which you may find useful):

* post about things that interest you, and include hashtags (for instance "birdwatching")
* boost posts that you find interesting from others - while there is no algorithm which those actions drive, it fosters connections as well
* spend some quality time finding people to follow - I love reading a variety of science topics, and I found a list of science journalists to follow on Reddit

On that last point, doing a more general web search to find mastodon users with whom you share interests is probably better than trying to find them on Mastodon itself.