With a simple java program, I send GET requests using YouTube Data API specifically videos.list, in order to get the public metadata of a video and store it as .json files.
If you go to the Google Developer console where you enabled the YouTube API. the second tab is called quota
Click the pencil next to which ever quota it is that you are blowing out. A new window will pop up with a link called apply for higher quota
.
Fill out the form to apply. To my knowledge you do not have to pay for additional YouTube quota but it can take time to get approved. Make sure you comply with everything on the form.
I have never heard of the one project per client term
. Technically you can run your application using different API Keys it should work fine. Technically there is nothing wrong with creating additional projects on Google Developer console. You don't need to go as far as creating another Google account.