The keywords meta tag is deprecated and not used by any of the major search engines, so don't even worry about that.
As for a general strategy you should focus on a keyword or two for each page and optimize for that. When you link internally in your site, use the keywords your optimizing for in the anchor text. When acquiring external links try to do this as much as possible. Don't cannibalize yourself by trying to optimize for the same keyword across all your pages.
I wouldn't worry about making landing pages in order to get them ranked - thats what your main pages are for. Use landing pages to test out what converts best with A/B testing, and as end points for your PPC campaigns.