In my opinion, if you are newbei and impatient about earning, probably you will rush for a niche. After sometime, when you realise writing for people is more important than writing for adsense. I believe money will come if you really be patient and decided about what you are doing. "Patience is a virtue my friend" as someone said... What is your opinion ?
i second that.. if u just stuff keywords with out making sense. its simply does not offer value........ its best to write good engaging content