Try to a Whatsapp Post regarding "WHAT TO STUDY? WHAT TO LEAVE? WHEN TO STUDY? ETC?"
Answer: A little Long, read with Patience
→ Thanks for sharing your query, I can understand your dilemma.
→ I will try to answer your question with an analogy,
→ Suppose you are living in Mumbai and want to goto Delhi.
Now, depending upon the urgency and the purpose of your visit, you will make your travel plans accordingly.
Some might choose the path of Flight, Some by Train, Some by Bus, Some by their own Vehicle, Some my pool.
Also, the stuff you will pack will also depends. So some only cloths are important, for some Laptop, for some documents, for some gifts, etc
→ Similarly, Cracking UPSC CSE is your goal, however your starting points might be different along with your different individual capabilities.
Thus, for some NCERTs are mandatory, Some can neglect it altogether, some needs only summary, etc.
Accordingly, regarding CSAT - Some need proper classes and some just need to practice as their basics are good.
→ Thus, I would say depending upon your capabilities, starting point and how much time do you have- you shall decide which things to pickup? which shall to drop? which to do partially? etc