For games you can use Admob with Chartboost/Startapp. A lot of people complain about Startapp, but for games, it gave me bigger revenue than Admob or Chartboost.
For apps the best is to use only Admob. Maybe Facebook Audience Network(the problem is that it has a really low fill rate).
Don't use Inmobi, Applovin - they have low ECPM.
Maybe you can try UnityAds for video ads.