I make more from Affiliates then Adsense, but the strategy you use has to be very different.
Direct linking doesn't work, nor does second click linking.
If you're advertising, but you don't own the product you don't have any control. Control over the price, quantity, landing page, etc.
The user most click your site, read some stuff, then go to the affiliate site and make the purchase. If a person is searching to buy, they don't want a middle man page, they want the Cost and the ability to buy.
People will click your ads, read a little and press the back button.
Affiliate income seem to only work when your site has some type of relationship based on adding value, not capturing buy keyword from Google "Unless you direct link to the merchant website and/or product page".
Now you can make a ton of money direct linking, but you have to find an Affiliate program that allows it, "or cloak you traffic so they won't know you are.