You can sign up as an Amazon associate straight away without a site. As long as you have the URL and it belongs to you. They won’t approve your site until you have made your first commission. So what I would do is get the site built and add all the content that you need. Make sure its finished. Then sign up to the Amazon associates, add in your aff codes to your review pages and then you just wait for your first sale. Make sure you read the amazon T&Cs so your site is compliant. If it isn’t then they will not approve your site.
Affiliate marketing overlaps with other Internet marketing methods to some degree, because affiliates often use regular advertising methods. Those methods include organic search engine optimization (SEO), paid search engine marketing (PPC – Pay Per Click), e-mail marketing, content marketing, and (in some sense) display advertising. On the other hand, affiliates sometimes use less orthodox techniques, such as publishing reviews of products or services offered by a partner.
Once you've protected your prospecting pool, maximize your affiliate program by working with the best and leaving the rest. As the old 80/20 adage implies, most of your revenue will come from a very small percentage of your affiliates. Because it can be time-consuming to manage a larger affiliate network, consider selecting only a few companies initially, and interview them before signing them on. Affiliates are an extension of your sales force and represent your online brand, so choose partners carefully.