Amazon site question.

Hello, I am currently building my first amazon affiliate site. As I understand from what I read is that I need 50% of my articles to be monetized and the other 50% to be just informational. So here is where my problem lies, I have read in one place that the informational content should be ranked by picking a good low competition keyword for it and in another place I read that it is not important to pick a low competition keyword for informational content and that this content only is useful to get accepted into Amazon affiliate program. So if anyone has any experience with Amazon sites, I would like some advice.