Some tips for starting a newsletter:

Don't worry about the number of subscribers, but rather the engagement. Open rate, etc. 

Learn best practices in terms of list cleaning and maintenance. Don't be afraid to remove people off your list and directly ask for readers to unsubscribe.

In terms of advertising and making money from your newsletter, it is ideal to have a newsletter that is sent more than monthly, or weekly. A newsletter with 7,000 subscribers that sends weekly will generally make the same money as a newsletter with 1,000 subscribers that sends 7 days a week.

Ask your readers to reply. This is good for open rates and deliverability. It also lets you talk to your readers and really understand what they want.

Spend some time on the design. Make it look nice, simple, and readable.

Look at the numbers aggressively. If open rates are going down, do something about it, ask for help.

Unfortunately, I learned all of these the hard way 😆