Advice on holding on to newsletter subscribers

I am accumulating new subscribers to my newsletter through group promos on BookFunnel. I am working toward launching my first novel this fall, and building my platform. I am aware that many people sign up just for the freebies, and am fine with that. In the month of this promo, I have gone from 25 subscribers, (that should tell you how green I am), to currently 112. I have lost 11, so had 123.

My quandary is how do I keep those who signed up through the give-away? I have a blog, but my newsletter has so far been just updates on my publishing journey…Should I include parts of my blog?

What has worked for some of you who have worked through this?