I've been very fortunate, in that I've been putting out my series only for a few weeks and I'm one away from 25. What I've learned more than anything is that in the early part of your time here, interacting with the community matters a ton! There are so many super supportive folks here on the forum that I know I wouldn't have gotten as far as I have without commenting and helping other folks out in Sub for Sub, or comment for comment style threads.
Second, I have a feel strong feeling from marketing experience that if you're writing for yourself, make as many stories as you want, but if you REALLY want to try and build your subscriber base, make sure to focus on one series and provide regular updates.
Third, there's a lot of gritty marketing SEO type stuff that could be used to analyze what genre your stuff belongs in or how to make the perfect cover, stuff like that. The best way to understand where your work would be most welcome and how to present it to people (if that matters to you) would be to go view the Popular and Trending lists where you think your work belongs. See what really sets them apart, and you can use that to guide you.
Lastly, make sure to talk to people outside of Tapas too. People are kind of antsy with the buyout having happened and executives making doublespeak, but a surefire way to grow your audience in to see if you can convince friends or family that aren't already on Tapas to join and sub to your series. That way they get cool stories AND to support someone they care about.