I've got some really good keywords for some of the cpa offers
that are getting a lot of traffic with little competition.

Whats the best way to setup a cpa campaign for organic traffic.

Should I create a domain for each keyword & write a review
of the cpa offer with a link to it.

Should I pick a domain for a group of cpa offers like dietreviews.com
creditreviews.com & review each campaign with the keyword in the
title & sprinkled in throughout the page & then paste the whole
campaign into the page.

Also will Google penalized me for dupe content if I don't change any
of the campaign but just adding some text on the page reviewing it.

I plan on using Wordpress for doing this & doing some social bookmarking
and pinging, along with some good seo.

With wordpress we can create html landing pages like a regular
web page.

Having keywords in your URL and domain name does help with google ranking. However, if you say you are already getting traffic with little competition you should weight the cost/benefit of registering a new domain name for every single offer. If it's a competitive niche it may be necessary, if not you might be able to get away with using keyword laced subdomains from a single top level domain.

You can use iBusinessPromoter to analyze your pages and see how they stack up and guesstimate how much a dedicated domain name would help.

The cost of the domain I don't care about it's the coversion factor.

I have to get the keywords on the page somehow, should I put them
in a review of the cpa offer & send them to it.