I started with "More" and built from there. Underlying is the default Clean theme from which More is also built.
Essential, Aardvark, and several other themes were used in inspiration as I basically took the elements we wanted for our site and put them all together like a soup.
Gareth J Barnard knows his stuff. I wish I could dig into all the various hooks and code like he does with his themes.
As a beginner, More is a good theme to clone and start from. I chose this as it will be included with Moodle as a default package so I can look to it when updating my theme for any changes.