Welcome to HTML5 game development. Here's the elephant in the room ... generic interstitial in-game-ads are worthless. $1 eCPM roughly means "if 1,000 players play my game I might get to share $1 with my publisher 60 days later". Does that sound viable even before we reduce it by factoring in odds of non-payment, cost of collection, ruining the player experience etc? Or, does any story of a positive experience suddenly make it a compelling proposition?
My general advice to newcomers is "make games for fun", and develop your own audience while doing so. First make a small game collect