be perfect with OR part, Marginal costing and standard costing... I suggest conceptual understanding of all the problems and theory questions.
ISCA dinesh madan is very student friendly.. try to read ISCA daily.. keep in touch with this subject frequently.
For DT vinod gupta sir books are very nice.. he explained each section with examples .. this is suggested when u have more time to allot DT or u have read the book earlier.. The day before the exam matters a lot.. U have to revise all the subject what u read . so select the book as per ur conditions.
IDT Bangar is enough
DONT MISS
selected case laws and amendments read atleast 2 Previous attempts RTPs
try to manage time at the time of preparation itself..
one very important point is read the question 2 or 3 times and do atleast some problems without looking at solutions. so that u can easily face new problems in the Examination..