Took a while to get to 300, but I'm now growing at between 50-80 subscribers per week without spending a single cent on ads.
I also started a community initiative last week to match subscribers who have similar interests with each other for a virtual chat. They'll have their first meetings this week and I'm so excited.
I shared what I learned when I got to 500 subscribers here: https://www.indiehackers.com/post/5-things-i-learned-from-getting-to-500-subscribers-9d5562f05d