I always tell people that mastodon is more like a garden than a grocery store.
It will not automatically start serving you any content because there is no algorithm.
If you want to begin to cultivate your feed, you should search for topics that interest you, especially using the hashtags. Post an introduction with hashtags (there are guides for doing this online). Then start following everyone who posts something interesting. If you find out later that they are not posting the type of material you are interested in then you can always unfollow in there no hard feelings. You can also follow or mute individual hashtags.
Most importantly, Mastodon is actually a social network. Reply to the people you follow, like and boost, boost, boost! Plan to be a participant in the conversation.