What do you use to promote your prototype in order to get idea validation?

Hello, my name is Serban. Together with a friend we came with an awesome idea - a mobile app that helps like-minded people meet in real life and have fun doing what they love. We've created a website for the idea, we designed some screens and now we are working on the code part. While it is under construction we thought it would be great to get some people offer some feedback on our idea, challenge some features and also maybe get some early adopters. How could i get to this? Posts on Instagram/Facebook? 1 minute compelling video about how the mobile app works? ADS? I'd like to know your opinion for I am in total darkness. This is the website for now: https://www.frienduin.com