I've used Google Adwords since I started with my affiliate program and it has been quite successful. The key is to learn how to use Adwords to your advantage. There are some tricks to drive quality traffic to your web site. You might want to invest a small amount of money to get some training on how to use the product.

There are other ways to get free traffic to your site too and I would suggest doing those as well. But nothing beats PPC for getting the kind of traffic you need to make the kind of cash you want, even if you want to just make some extra cash every month.

Hope this helps.