Welcome #TwitterMigration!
First things first, as you acclimate, there are a couple of important points.
1. You'll get the most value in the early days of use by scrolling the Local and Federated timelines, not your Home timeline. That will fill up as you follow accounts and hashtags.
2. The Mastodon app on iOS and Android makes it really difficult to find those other timelines. But there's great news! You have other options! On Android, look for Tusky. On iOS, look for Metatext.