Need advice about app advertisement

Hey! If you had health&fitness app, how would you advertise it using sources besides main like fb/adwords/tt/snapchat..., to make advertisement viral and cheap?

Reddit can be a good source for free traffic if you know what you are doing. For example, once i saw a thread in r/disciplined where a guy told a solid way to be disciplined. He also added how his app could help people be more disciplined in a very smooth way. And i saw 100s of people commenting saying the app is great.

Reddit ads is definitely a good option, you can also try in native networks like Taboola and Revcontent.

First of all app has to be highly retentive. Different promotion options will be useless if app is not engaging people. Remember that 70% of installs come from search. If you have eye-catching screenshots and icon + impressive promotional text you will definitely have installs.
All the sites like Reddit, Quora, HackerNews, ProductHunt are brilliant free traffic sources if you are ready to share useful unique content with audience.