Adsense is not a PPC network, Adwords is and since Google has the most reach, go for adwords. However, that also means the prices/competition will be higher, so never discard yahoo/bing or second tier ppc networks (f.e. 7 search). You won't get the traffic there but bid prices will be lower as well.
The CPA business is HUGE. CPA stands for Cost Per Aquisition, which basically means, someone is going to pay you for every lead they aquire. That lead could be a new customer, it could be a new option, or it could be something as simple as someone providing their zip code and other. The right affiliate program, especially a CPA network, can turn you into a money making online publisher. This CPA review will give you great ideas about how to make money online. You won't believe just how easy it is to make money online, thousands are already doing it, and this is a tried and tested method. Pay per click marketing, media buys, CPV these are used to generate more money. You need a budget of at least a few hundred dollars to do CPV or PPC.
I have used Google Adesnce, ClickXChange and CJ.com programs and I've earn goog money. Google Adsence much expensive.
CPA = Cost per ACTION / not aquisition Google Adsense is NOT PPC / Google AdWords is. I find that others have found solo ads very useful. anyone else?
adwords in the us can be expensive but sometimes adwords in other countries is much cheaper and gives good ROI