Over the years I have seen a ton of Amazon affiliate sites, most of which never make much of anything because they never rank in Google. The best traffic for most physical products listed in Amazon is going to be search.

Not email lists (how do you get someone to your signup page?) Not social media. Not PPV. Not PPC due to the expense and Amazon commission rate. Not forums. But search.

Different products may rely on different traffic funnels, but as a "general...