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Once you have established which of the 2 or 3 ads in the ad group is doing the best (say by a margin of at least .5%) then launch one or two new ads that are variants of the one that has the highest CTR.
The best way to do this, imho, is to also track backend conversion...that way, you can optimize the whole set of variables, from beginning to end, with time.
then in your log analysis tools, track those or cookie them based on their initial referrer. it won't 100% flawless, but it will work *most* of the time.