What is the best type of coding best for Knack?

I am starting to need more and more additional coding requirements for my Knack DB's...both in functionality and display (CSS).  While I can some minor changes myself, I need a better understanding of coding in general to make significant functional changes.  Can someone recommend the best (for Knack editing) type of coding course I could take?   Javascript, CSS, or whatever?  

 

Thanks.