It is very difficult to earn from Amazon and Ebay. The earnings from Ebay is included with Hubpages Ad program. You can get success with Amazon if you write Hub based on specific product to see it. Google adsense is good when you don't use Hubpages ad program.
For me the best source of income is Hubpages Ad program. Currently I am earning near 15 dollars monthly from my 28 Hubs. I hardly earn anything from Google adsense.