The most useful thing I can contribute is rather basic, but fundamental to playing with css:
step 1: Learn how to select a component: CSS selectors - CSS: Cascading Style Sheets | MDN
This doesn't mean memorize everything, it means learn how it works and how you can use a search engine to find the selectors you need.
step 2: Use the dev tools to find the element you want to style, then apply step 1 to target it.
That's where the "advanced" (meaning beyond perspective classes) css journey starts.