You can use Google Analytics to find best performing keywords and shift budget to the highest converting keywords, but if you're looking to expand your keyword lists; you can leverage free Google tools to optimize your marketing campaigns beyond Google Analytics, Analytics Blog.
- Look at best keywords in your Analytics Keyword Report.
- Input these keywords with your site URL into the Search-based Keyword Tool to find keywords, currently not in your AdWords campaign.
- For each keyword identified, use Google Insights for Search to see where regional interest is highest and better optimize through geotargeting. You can also enter your top-performing keywords directly into Google Insights for Search to identify the top-related and rising searches.