trying to promote clickbank products.

Well, If you would like to business in the Internet marketing section , you should buy a Domain & Hosting to do the business for a long time.Without having the website, you may not gain in this as you expect for a long time. You can join many facebook fan page & post about your product, You can use some relevant Forum posting & relevant blog commenting of your site. Then you will be able to increase your site traffic. Anyway you should do some SEO to increase your site traffic & page rank. You need to make strong your site. Thanks a lot.

A product is a product. Learn the essentials of internet marketing so that you can learn how to sell ANYTHING successfully online. Guess what.... you're only the right forum to learn how to do this. Go into the War Room and read books on this particular Clickbank subject. This will give you a fast start and bring you up to speed on things.

Different markets, different niches, different traffic sources.

I don't think it's possible to say whether one traffic source will or won't categorically for all Clickbank products.

It really is a case of testing, putting some money on the line and being willing to lose it in order to get results so you can then start doing things right.

I know that can be tough to get your head 'around it but that's the reality.

Decide on what you're prepared to spend (or lose) to get results for a traffic source. Test, tweak, test, tweak and so on.

The answer to your question is "It depends..."
Regardless of the PPC network you will need a budget. The size of the budget required will depend upon the targeted keywords, the scope of the campaign, and the duration. Use caution with PPC until you are familiar with the process. You can lose just as fast as you gain if done wrong. As far as network, that depends upon the niche and the offer as well. Certain demographics favor one while others prefer different one. If going this route, start small and test. when you find what works then scale up.
Solo ads can be a tremendous list builder but your traffic will have to go to YOUR landing page. That means you will need your own site for starters. (You should have one anyway). Most vendors will require some sort of a freebie offer on the landing page. You can always link to your product offer on the thank you/ confirmation page as a way to gain immediate sales. Again start small and test. scale only when results dictate.

Regardless of the method, you will need to do some homework before clicking the order button. Look for testimonials (be sure they're real). Get referrals from others who have done that particular method (ask here for example). Start small, test, test, test and test some more. Scale up only when the response rates indicate that you have a winning combination. Don't be surprised if you find that you need to craft your own opt-in devices, landing pages, follow up emails, etc as many product creators don't get the combinations just right. The good news is that those things aren't all that difficult and finding information on them is a breeze. study up, ask away, test, test,test, scale.