That’s the million dollar question, as your only metrics you have are dragon prints & reviews. (There used to be “ratings” but that got abused by trolls.)
What I do is I record my dragon prints, daily, and plot them in a spreadsheet; I do this with all my AFF & AO3 stories, and it lets me know which stories gain X number of hits after a chapter post, that’s about the only way to measure interest.
Now, the other thing you can do is to read stories, drop reviews, and hope the karma comes back to you. After all, a review is golden.