From my perspective you cannot make money unless you are pumping out 100k users a month, use something like amazon to make money if your website has low volume. i have 3 blogs and ppc is rubbish for me. Amazon and a few others like it are much better. It's not difficult either, amazon give you all the tools you need, i dropped ppc long ago and amazon treats me good.
I would suggest CPA & Affiliate Program, because you can get a lot of money without your visitors spending any at all.