I think if you're going to write a blog you need to think of a way to promote that. So you end up promoting something that's promoting something else. And you've said you don't have your novel finished yet. So if you're talking about characters or an inspiration for an unfinished novel, what is there for a reader really to connect with?

So find a way to add value. Maybe talk about the characters in terms or writing, why this character is or isn't effective. Then you're talking about something else, but in the context of your novel. If you do this then you can go about promoting it on social media, like pinterest or something like that. If you write a blog about protagonists and talk about your protagonist in it then people who are solely interested in writing might become interested in your theories or ideas and get interested in your blog, and ultimately, your novel, that way.