Would you mind sharing your blog? I'd love to give it a read and give you some feedback. For me personally, it's easiest to write about things I'm passionate about. That might be related to my career or to my life in general. Each one has a different target audience. Understanding that audience is key.

Websites like Hacker News, Reddit, and others provide you with a platform to have your content seen. That doesn't necessarily mean it will succeed, though. I think the biggest hurdle is producing work you would consider high quality. Your readers need to feel like they've learned something valuable by the end of the article. It's difficult to accomplish that while still keeping their interest and not writing a book. Hopefully this helps answer your question a bit.