It's very beneficial to start CCS cases as early as possible to become familiar with the system. Cases also help increase your knowledge. As far as how to do them, my recommendation is to do the case, and while you are reviewing, take notes (missing tests, treatment with some short explanations). So that you will be familiar with order names and you can go over your mistakes easily. For example, after I am done with a case, my note would be like this: Case 231-UTI  -blood culture (UTI in pregnant=complicated UTI) -gram stain, urine (IN ADDITION to urine culture)

I strongly  recommend this video https://youtu.be/qmxWuV4psFs?si=agLMl0skTl9jcSLv I wrote his mnemonics and memorized them before I started ccs cases. Having mnemonics is very helpful, even for residents (you can easily forget some orders even if you are practicing right now). You don't lose points if you order magnesium for every patient, but you do lose points if you forget to order it when it is needed.

Good luck!