Important areas-select case laws for customs and excise?

In my opinion there cannot be done selection while you are doing Case laws from ICAI book.

My advice to you is to give one effective hour of your day to the supplementary book of ICAI dailyy and in 20 days you will be able to complete the whole book of IDT case laws itself.

try to study it with correlating provisions of the act and at first sitting study the whole matter and then for exam day keep only decisions marked so that you will be able to finish the whole case laws within 1 or 1 & 1/2 hour.