Advertising on Amazon?

Not used that, probably wouldn't either to be honest. When I start marketing I will be doing searches on google for relevant words then contacting sites on the first pages of organic results about advertising on them. The search words for non-fiction with it's established subect matter will be easier while fiction more tricky. This might be something you could try, I don't think it would be more expensive than what Amazon would charge, maybe cheaper.

Have you ever bought a book because of an ad on Amazon?

What makes you think anyone else will?