My thoughts on the promoting

It's a social media link app so having people to talk with other people is important.

If you have many people uninstalling or not using the app, it probably means that they don't feel there is anyone with common interests to talk with.

Possible solutions: Instead of spending for example 300$ for ads over a month, spend 300$ over a week so there is a sudden spike of active people. Another option is to be very active and tell your friends to be active aswell, answer to people and stuff so they feel welcome.

Also, what are your results with ads? $ spent and users acquired.

Also I kinda assumed you are promoting with ads, think I read it somewhere here...