In my experience, if you want to make money of Adsense (but not through an MFA (Made For Adsense) site) it´s simply a number game. More pages means more visits means more clicks means more money.

Optimizing for those couple of phrases that will bring in visitors by the hundreds of thousands,.... little chance.

It´s all about content. And make sure it´s not MFA. (i.e. nonsense content without any real value)

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Otimização de Sites (SEO in Brazil)