It can be hard to bootstrap yourself up from zero followers. I’d recommend posting something just so that people have an idea of the kind of thing they can expect if they follow you from checking out your profile. But you probably won’t get much engagement from your own posts at first, so it will probably be more fun to just reply to other accounts.

Bluesky has a feature where you can set up customized feeds to filter for any kind of content you want. The person who saw your post might have seen it in the “newskies” feed which just contains every first post that any account makes for example. So one way to get engagement can be to write posts that show up in a certain feed that people follow, like there exist some feeds that are based around certain topics that usually trigger based on your post containing certain keywords. Most people just use the following feed though, I think.