Ask HN: I'm building an audience on Twitter. What's next?

Hi HN!

Instead of building a side project, I've decided to try to build an audience first, and then build a side project for them. I've worked on this for 1h per day for almost a week now, and I have 150 followers on Twitter. They are real followers interested in a specific niche market.

My question is: what's next? Should I keep building my number of followers? Should I make a blog? Should I try to make them sign up to a newsletter? Should I start asking them questions about potential problems they are facing that I could solve?

Thanks!