just use my most clicked ad?
add more keywords?
change ad copy?
If you're getting an average of 4 cent clicks with a 1% CTR, it sounds like you're in an area without much competition. You may be getting all the searches that come in for those words as it is. Google can only deliver if people search.
As HumbleBeginnings suggested, refining that list with more relevant keywords and variations may bring in a wider range of visitors. That is, if there are indeed more prospective customers that you're missing out on. They could be searching for your product or service using terms that you haven't stumbled upon yet.
Trying new keywords and testing (not hastily changing existing ads!) new ads should always be an ongoing process to improve ROI.
Israel