First off, my tips utilizing ads for Amazon.com and Ebay.com will be the same as the tips for Ebay.com and Amazon.com. :) I couldn't help myself!
I understand your frustration. I am not sure you are doing anything wrong other than perhaps not relating articles to things popular to Amazon shoppers or Ebay. For instance, Kindle is a big deal now. If you had an insight into something or some feature of Kindle and explain that insight well, it should bring Kindle lovers to your hub. I believe I have seen my Ebay clicks come from folks interested, let's say in prospecting, and then noticing deals at Ebay on products also relating to prospecting but perhaps not their main motivation for coming to the article. I think it is impulse shopping.
When I started out, I signed up for Amazon and Adsense (Ebay wasn't interested I think since I hadn't many hubs or experience?) For months I got no clicks on Amazon.com ads. In fact, I have never gotten a click in 2 years! After awhile I just gave up and stopped the ads and went exclusively with Adsense. Then, I started to make a "little" more money. When the HubPages Ad Program came out I signed up and my earnings jumped again (I still was signed up with Adsense).
If it were me, I would forget Amazon.com (understanding that there are probably people making good money off of it somehow) and focus on Ad Program, Adsense and Ebay.
I make sure I don't put more than 2 Ebay ads on a Hub because I think three + gives the impression that the article is "spammy". That is, it gives the impression that instead of being focused on writing, you are only interested in a dollar. I actually believe if folks come to your article and see at first glance a bunch of ads, they are many times likely to just check out and go somewhere else. That's just my unscientific opinion.
Don't be too disappointed. Working hard at it really does improve your results. I almost make $1 a day now after 55 hubs and 2 years of participation. Not sure that will last with whatever is happening with the Google search engine because my views are dropping too. But, then again, we have seen that before, also. Hang in there!