How to get the first 1000 subscribers for your newsletter?

I run a newsletter called "The Big Bang Launch" Newsletter where I interview makers whose products ranked top #3 on productHunt and share their launch strategy. We have 550 subscribers now but it took more than 5 months and 15+ issues to reach here. I want to know how long it took you to reach the first 1000 newsletter subscribers and what are the top ways to get new subscribers for your newsletter? PS: Here is the link to my newsletter: https://thebigbanglaunch.substac...