I just published my app, "3316 Challenge" in the Google Play Store. For the advertisement, I used just like this, Construct 2 + CocoonJS + MoPub + AdMob. I faced some problems during this project, but I could fix all of them. Here's 2 important tips. You can try my game(down there) for the example. I didn't used fullscreen ad.
1. Don't use ad from MoPub Marketplace.(Important)
Advertisements from the MoPub Marketplace sometimes make your game screen black. I don't know why, but after setting it off, it runs nicely(You can set it in the MoPub - Network tab) Make your banner show the ad only from AdMob.
2. Show/Hide the banner ad at Every tick
Sometimes a banner ad just pops up when it's ready, ignoring your setup. So make it firm with the Every tick event.