Running a blog is an investment. Though not pricey, you’re investing a lot of effort into it, assuming you’ll find an audience. Without much harm, you may wonder how you can reach your audience. If you’re going to lose something else, you will get every chance by concentrating the blog on a niche.
A niche is a limited topic with a following but less competition. “Investment” is too broad of an issue. There are different types of investments that can yield better results, from stocks to cash, and focusing on that can. You can make the subject more specific. What about writing on a budget regarding stock investment?
Think of a subject you’re interested in, and use Google Trends to see if an audience is there. If the results are too low, then expand the item and vice versa.