Yes, I understand. What you are looking for are interstitials (ads that cover the entire screen) which produce significantly more revenue than banner ads (which cover only the bottom/top of the screen), but still very little revenue in comparison to video ads or interstitial ads that weren't implemented in C2, which makes them perform badly.
Your event sheet should look like this:
[quote:2td9ik59]On game over -> (AdMob) Preload interstitial
(AdMob) On interstitial received -> (AdMob) Show interstitial
Problem is, C2 games load very very slowly AdMob ads (3-5 seconds with perfect internet connection, way more with bad internet connection) so I would suggest to preload your interstitial ad on start of the game (On start of Layout) and trigger the ad on end of the game.
NOTE: You also mentioned something about rewarding users for watching an ad. AdMob rewarded ads would be the best solution, but official AdMob Plugin doesn't support this feature.