How to properly promote a mobile application?

Question

Marketing

Hello! I am making an application for iOS, I plan to release it in the App Store soon. The question arose - how to promote it? Catch up with an audience? How to generate content initially, given that the application is something like Avito, respectively, if people download it, and it is empty, it does not fit. And is it better to launch it first in one city (for example, only in St. Petersburg) or throughout Russia and the CIS? If anyone has a similar experience - I will be very grateful for advice and answers.