If you want to discover posts and accounts about specific topics, try following hashtags.
When you follow a hashtag, posts with that tag will automatically appear in your main Home feed even if you don't follow the person who posted it. For example, if you follow #Dogs you will start seeing doggos appear in your main feed.
To follow a hashtag, search for the tag and then click the follow button in the top right corner of the screen.
For more details see https://fedi.tips/how-do-i-follow-hashtags-on-mastodon-and-the-fediverse