There are quite a lot of bloggers who are in favor of keeping their topics very narrow. That’s the traditional niche approach.
The idea is to focus on a particular product and the specific market. That might work for you and in fact the might be what you want to do.
On the other hand there are also expert marketers like Jimmy D. Brown, who suggests that it’s better to be a little broader and basically draw an audience with certain interests, such as, for example, self help.
The idea here is that they might have additional, related interests as well, so