Many people create huge affiliate sites using product feeds. The problem with generic well-used feeds is that many other people will have the exact same content. Since Google does not desire to show multiple copies of the same content, most of the affiliate feed sites end up not getting indexed or are quickly removed from the search results if they are indexed.
Some people end up adding RSS or other content to the pages to make them look unique, but Google also employs remote content raters to evaluate sites. If the site looks like it would not have a functional purpose outside of the affiliate program, Google does not want it in their index. The instructions Google gave remote content raters for determining if an affiliate site was useful was “is there a value-added service that would make users want to visit this site instead of the original merchant site?”
People do not usually buy from affiliate banners. A better way to create affiliate sites is to create unique original content with what looks like unbiased reviews. Whether you are affiliate marketing or creating your own merchant site, each unique item or idea should have its own unique page with sufficient unique content on it. If the only difference between items is size or color, then you might run into duplicate content issues (if pages are too similar, then Google may assume they offer little value or are of poor content quality).
Lots of people offer sales letters, but if you create what looks like an original, thoughtful, and honest review, you can send people to the official sites using text links from within the reviews that convert exceptionally well. The less automated your site and SEO techniques are, the greater chance it will do well in the long term.
Many large affiliates also hide the affiliate links to make it harder for people to steal their affiliate commission. Some people think Google hates affiliate marketers. They do not necessarily hate affiliates, but they hate unoriginal or useless content cluttering their search index. Most affiliate marketing sites are thin sites featuring duplicate content.
If you are new to the web and do not have much money to work with, one good way to save money is to sell things to yourself using your own affiliate link. Some merchants may not like this (it may violate some affiliate terms of service. If you can save Rs.500 for ten minutes of work, why not do it?