Try promoting something you are interested in and promote it. There is a market for anything you can think of. Some are more in demand than others, but you can still make money off of a less in demand niche if you make sure people find your website first and make it better than the rest.
If it's your first website, then write about something you like (hobby). Most of us have started that way.
Yes, you really should write about something you like. Later write content that solves peoples problems. And there is like gazilion problems that needs to be solved. Starting from how to wake up in the morning or how to contact Google. Sky is the limit.
Try to start with one of your hobbies, or topic that you have much knowledge of, so you can write a lot and quality articles,that will bring people to your site. As said before there is interest for anything you can think of so with correct promoting of your site and bringing traffic you dont have to be afraid about not having a interest.
On which Niche can you write lot of content? I suggest you make a site on that Niche. The real thing is the amount of content that you can write. The more you write, the more traffic you will get.