It's not a question of "how to get good keywords" or "the wrong keyword on my homepage". Keywords are simply the words or phrases that people will type into a search engine when they want to find some information. The right keywords for your site are those that describe the main theme or subject of the site - or, more correctly, of the individual pages in the site.
Just concentrate on writing the best possible content for you site, and make sure it includes the keywords you think people will search for.
And don't worry too much about the home page. As far as SEO is concerned, the home page is just another page on the site. Given that yours is an affiliate marketing site, the important thing is for searchers to find the pages that give you the best conversions.