If you want to start a nice blog, then why not start a blog with stories about Fiverr.
You can create a lot about your own experience with Fiverr. (As a buyer or as a seller) But you can also let others talk about what they think of Fiverr and the gigs that are offered on it.
But you do NOT have to limit yourself to talk only about Fiverr ! You can make also a blog in general about experience on Freelance websites. And interact with people about this subject.
As mention, it is just a blog idea that you can take with you.And use it for a new blog !