It is not required to have Hubpages ad program to earn from Amazon. This is the only earning site that you can use without the Hubpages earning program.
Once you have applied for, and been accepted to the Hubpages earning program, then you can apply for Google adsense. Google adsense is the ads that generate the most traffic and therefore earn you money.
Before applying for Google adsense, write at least 15-20 rich hubs that people will want to read and Google will want to place their ads on. If you are from India, China, and a few other countries there is a six month waiting period for Google adsense acceptance.
Just write good quality hubs and be patient. You will eventually be accepted. Good luck!