I made an app 3 months ago, only 30 users. None convert to paying customers. What am I doing wrong?

I made an app from scratch for android. I was hopeful, but didn't get any reach whatsoever. It's a sort of productivity app with journaling features. It's called unfog. But I haven't seen any traction so far. It's been 3 months. I don't have the budget to market. What other options do I have? Or is it just a lame idea?