Yes Ryan6 is right, it's very hard to earn with common niche. You have to choose the niche in which you can get good CPC rate. and I think it's hard to get good amount of traffic on blogspot, rather than try to get your own domain.
What this guy said. You'll need a high unique visitor count in order to make any money along with good ad placement. But it is hard to be honest. I would just focus on promoting your website adding new articles. Also think: What articles would your potential users like to see? What would interest them?
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