Narrow your action / marketing focus to get started. Perhaps see if you can promote your app at destinations (to the co-benefit of the destination / place if at all possible; tell the owner you'll market their business on your app in exchange), rather than focusing on trying to get users outside of active context. Go to where the activity is occurring, where people are doing the thing you want them to use your app for (eg at a bar). If you're willing to grind, that approach is probably your best bet (short of a huge, expensive ad blitz). Where people are doing the thing in question, they will be most receptive; outside of that, their receptivity plunges toward zero (unless referred by a friend in the moment of / before / during an activity).
You better be a very social type, because you need to be out in the thick of it. You need to be of the people, in it, pushing this thing to every human that will listen at every location that will tolerate you. You need to be the social manifestation of the result you want out of the app (since it's a very social app by its nature), network user after user after user. This is an example of doing something that doesn't scale, you're going to go out and sell every initial new user on the app, where the app is going to live most of its life (at destinations, events). After a while, the snowball momentum will take over, if you're lucky, and you won't have to grind for every new user.
Messaging people is a dead-end in most cases. It's like a spam email or cold call in how it lands in the brains of the people receiving it. Go to where the action is, sell (promote) your thing in its proper environment.