Of course there is absolutely no answer to this question.
If you know "what to write," then I have to wonder how good what you write will be in comparison to the competition; it's my opinion that if I want to get paid, then I have to be prepared to be THE BEST in the niches in which I choose to write.
From the way that you mentioned the $50.00 - I have to assume that when you talk about payout that you are, in this case, talking about a payout via the Hubpages ad program.
I would like to give you a helpful answer here - but I don't know if it's possible at all. I already had over two hundred published hubs when that program started. I've probably only published three or four since it started - but I think that anyone else that leaves an answer here - will have been a long time HP person, else their answer would be worth even less.
If you know good seo stuff then you should well know where your ads should be places, and so you should know what NOT to do so far as the layout and creation of your hubs entails.
I have to say this: Trying to compete in high pay per click niches is stupid unless you are positive that you are truly better than anyone else - and then you demonstrate that. The smart money is on the mid range pay per click keywords.
Personally, I've never looked at keyword research at all. I know what subjects I can compete in - and I don't even want to know what their pay per click is likely to be, because I want to be known as a good writer, and someone who is a nice guy, that comments back, is friendly, and is a damn good storyteller.
When I make money - that's great. When you make money -I'll cheer for you, but please have some integrity in your work.