I am using clickbank on my 2 sites and literally it was difficult to earn with them in first few weeks..because it needs a lot of promotion of your site and even after that its never sure that users will be purchasing the products..I'll suggest you to start a site in a high paying niche..this will assure at least some earnings from clickbank than none..I have made just 3 sales with them worth $29+ in commissions..It is easy for me to sell my products than to make the products sell for others as an affiliate..so, if affiliate program doesn't work for you, try their publisher program..I am earning $300+ on an average with the publisher program alone..