Narrow down the topics by reflecting on profitability and other goals. In order to make money, you'll need to find a niche that other people haven't filled already, but is still popular enough to attract a significant number of visitors. Also consider other factors, such as money you'd have to spend if your blog focused on reviewing products that you in turn would have to buy.
If you are using a free blog hosting service instead of your own domain name, you must provide high quality content with a limited number of relevant links or risk being shut down. If you are only interested in writing short, quick product reviews in order to earn money, you will need to host your own blog. Be warned that low-content, high-link blogs are a less reliable, though lower effort, way to earn money.
Your newsletter is all yours. Unlike with social media websites like Pinterest and Facebook, your newsletter and email subscribers are all yours, and you have their undivided attention. You don't have to worry about some social media algorithm not showing your content to your readers, as they are your email subscribers so you aren't fighting with anyone else to have them see your content.
Hi Sam! I love your site. We should definitely connect. I’m a school counselor and recently launched a site for parents to address pertinent teen topics. Like you, I struggle with the ultimate service I’d eventually offer on my site, but Ramsay’s idea is a great start. He’s absolutely right that people are looking for fresh content for their sites! Best of luck to you and I hope we can collaborate.