OP, don't go with PPC for this site if you only have $500. As already been said - you will lose it. Definitely do NOT waste it on 1 or 2 products, because its unlikely you'll find something that works off the bat. At 4%-6% payouts for Amazon products you need expensive items to make PPC work and those are mostly very competitive.
Create several separate review sites for products that are hot on Amazon. Nothing really competitive like iphones or cameras or anything. Look for items that are up and comers and not hammered yet. Consider seasonality (check google trends).
Then SEO the fuck out of those sites, write articles, squidoo lenses etc, comments on blogs. When you find sites/products that convert THEN add PPC campaigns for them, targetting specifically down to the MODEL, not generally by brand or products name. And do that on Bing and Yahoo, because unless you have lots of content on your site you risk having your account banned by google or in the least having your campaigns slapped (Ive had an account banned that only ever had 2 amazon affiliate sites, both of which were also slapped after I ran campaigns for about 2 weeks).
IF you had money and experience you could go the other way - you PPC to find winners, then SEO optimise for the winning products and keywords. Seeing as you have no money or experience take the slow approach.
Expect to fail repeatedly finding your winners.
I'd recommend you join Affiliit.com, they focus on review sites, seeing as you clearly clueless and need your hand held.