There's no best PPC/CPC, you simply have to test till you find what works well for your audience. Other factors like ad placement will definitely play a role as well so make sure you consider that while testing.
You can start with what Harry has already suggested then simply test different Ads till you find the ones that work best for your audience.
All I'm saying is that there's no one size fits all, what's best for me will not be best for everyone.
You can also survey your audience to find out what they want to avoid guess work. Then place Ads that are related to what they want and keep testing.
Check other blogs and websites in your niche to see what type of Ads they use and how they're placed. Check as many as you can (would be great if you can compare these sites with your survey results), then simply swallow the meat and spit the bones.
Go to Flippa, in the "just sold" section filter the results to ad revenue (remove affiliate and other revenue streams) to find sites that are making money through Ads. Study them and if the site sold well then there's a higher chance that person is doing a good job and you can learn a lot by just browsing these sites/blogs. This is time consuming though.
But hope it helps.