There are three areas to consider:
1. What is the conversion rate on your website
2. What is average margin per sale
Once you answer this question you should understand the target CPC you need in order to make money.
3. Lifetime value of clients
You may adjust the previous CPC to allow for repeat business.
Action List:
A) Given you already have identified keywords that are making positive ROI. Try split testing new variations of ad copy to increase traffic - without paying more.
B) Other keywords generating sales below target ROI - look at reducing bids to hit ROI targets
C) Look at Match Search query reports for the actual terms generating sales - build these into own adgroups with tailored ad copy to increase traction
D) Add negative keywords - this should help remove unwanted / irrelevant search terms. this will increase CTR's and improve quality scores = lower CPC
E) Check the times when conversions do & don't come through - adjusting times the campaign is running to be in line with when you get results.
F) Review device performance - consider adjusting mobile & desktop bids
