Ask HN: Got a working MVP. Now what?

Last week I launched my new MVP (https://wwww.flagspam.com). Already got one corporate customer and I'm trying to see if there are more potential customers out there (I know having just one client is big red flag).

The main problem is that I don't know where to get started or what should I do. I found this list: https://github.com/mmccaff/PlacesToPostYourStartup, did a couple of posts but wasn't very successful. I think my potential clients are startups who haven't developed a content reporting system yet, but I don't know where to find them.

I know Dropbox started with a landing page and a YouTube video, but how did they do to make it viral? Did they use ads? How new companies end up in tech blogs like TechCrunch (I know isn't a good example)?

Thanks!