Sorry if this bursts the bubble a little bit, but I'm sad to report that manually tagging your posts is not a super prominent source of growth. Tags can describe the content you publish, but over-optimization of them through manual tagging won't really make much difference. As ever, the best way to succeed on Substack is to do great work, consistently, and make sure people know you're doing it. (I made an edit to this comment after a colleague clarified a couple things for me.)