Steph Locke shares some experience on keyword bidding without breaking the piggy bank:
To be able to do the next stage I was interested in a solution that would give me an API or a bulk-upload interface for free or cheap. Google Ads has a Keyword Planner but having to create a campaign before I could even get started wasn’t fun. Another recommendation I’d had for keyword analysis was ahrefs.com and I noticed they had a $7 trial and an API that looked well documented. The API didn’t seem to cover keywords but it did have a bulk upload capability.
Some of what Steph’s doing is possible within AdWords reporting, but they will tend toward finding helpful ways of maximizing your spend.