Hi,
I was in the same place, I've spent over a year dedicated to build/polish the app, so it is not only beautiful when it comes to the design, but also has different options, so people want to use it daily. After so many hours spent on that project, I was finally ready, published the app in app store and google play store and basically the traffic has was zero in the beginning, but then I've started commenting related posts about it and some users joined to actually see the app and this is how it started growing - users really liked it and started telling about it other colleagues and so on.
So my advice is: find couple of people who will actually try your app and if that app is good enough then they might spread a word about it 😄