As any successful blogger will tell you, a blog is only as big as it's follower base. You can have the best blog idea in the world, but if you have no audience, you won't amass much readership, and even less revenue. Lucky for you, we live in a time when it's easier than ever to start a blog and get followers, as long as you engage socially.
What do I mean by that? Build your fan base on social media. What I DON'T mean is that you should spam your personal Facebook and Twitter 15 times a day with links to your blog. Nothing is more annoying than constant, pointless linking.
Determine exactly who your audience is first, and find a way to connect with them. Running a blog for fitness? Follow accounts that dedicate to the subject, participate in relevant trending topics, and engage with the community. Of course, you should also post small samples from your original blog content (with a link of course) to draw people to your site. People like content, but they also like brands that interact authentically. Pay attention to what your base asks for, and how they use social media.