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.

1.  Look at best keywords in your Analytics Keyword Report.
2. Input these keywords with your site URL into the Search-based Keyword Tool to find keywords, currently not in your AdWords campaign.
3. 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.