It really depends on the vertical that your app is trying to target.
I always find that Facebook is pretty good with re-targeting, and boosted posts (but only putting $2 per day on a post).
Engagement increases with image & video. Live video seems to always end up coming to the top of the feed (at least for me) and users are more forgiving about the content when it is marked as live.
For me, referral options inside apps has always been a good way to increase the number of users, but first, you want to ensure that existing users will use your app say 4-5 times and have a duration of 'in app time' of greater then three minutes.
It really depends on the vertical that your app is trying to target.
I always find that Facebook is pretty good with re-targeting, and boosted posts (but only putting $2 per day on a post).
Engagement increases with image & video. Live video seems to always end up coming to the top of the feed (at least for me) and users are more forgiving about the content when it is marked as live.
For me, referral options inside apps has always been a good way to increase the number of users, but first, you want to ensure that existing users will use your app say 4-5 times and have a duration of 'in app time' of greater then three minutes.