How to make your app popular among users?

Good Question, If I'd say practically, there no need of spending a lot of money and energy on marketing, logo, design etc etc etc. only you should have good quality content in your app, content means if you are creating an app for fitness so you'll have to make it very user friendly and effective like KEEP training app, I would suggest you download this app and use it for 2-3 days you'll be able to understand what I am saying, they have made fitness very easy and effective every single page of this app they have made very simple and they also post different blogs on a daily basis related to fitness and I have never seen a single add about KEEP training and Special logo or designing etc. The only thing they have done is they have made their content very effective and useful. HOPE THIS HELPS SIR.