Ask HN: Need an advice on the best platform to promote my mobile app/game on iOS

I have been building apps/games for 8 years as a hobby but have been out of the loop for the last couple of years when it comes to app promotions. The recent mobile game I've built is getting a decent amount of organic installs but I would like to boost it up the iOS charts a bit more with paid promotions. Does anyone have any experience with any promoting platforms that bring genuine user installs that are affordable in term of CPI? Preferably targeting tier 1 countries (UK, US, Australia, Canada and New Zealand). Any pointers and advice will be greatly appreciated.