When Taylor Swift was starting out and she said she wanted to sell 500,000 albums, she was advised that a good starting point to achieve that goal would be to introduce herself to 500,000 people. I think that's a good principle to start with, if you want 1000 subscribers be prepared to talk to at least 1000 people about your channel. Some might not be inspired to subscribe, others might want to share your channel with several of their friends who might want to subscribe too. The numbers are helped along by time and dedication.
Also, don't forget the 'call to action'. I started telling (asking?) people to subscribe and it helped. I have an expat chat forum and also just went on YT and told people they need to sign up... and they did. Nothing wrong with straight up asking, just don't be annoying about it.