I created the website http://drivingtests101.com/, a free driving test prep website for all vehicles types across 11 countries, this past year, as well as mobile apps for 4 countries.
Lets take a look at the website only. I believe the quality of the product is very good and this is proved by reaching the #2 downloaded education app in a country. However, despite this success on the app side, it was very slow on the website side because it was not marketed well, no one knew about it and no one could do find it.
In my experience, it is very rare for a product to become truly viral from the start.
If you want to grow fast, you need to spend resources on marketing to reach your customer, whether it be through paid or non-paid (eg - social media) means, although every case is specific.
For the website, spending money on SEO and taking the time to write a few articles increased traffic tenfold in the first month!
You learn by doing, but I would highly recommend throwing a few marketing things against the wall to see what sticks.
Good luck!