Dear frnd, its best that u hv planned smthing in s good way.
Costing, ISCA, DT and IDT.... these are the subjects u hv to study.
Costing classes its ok, but u require some more practice from reference books like Parag Gupta
ISCA is a biggest demon here, u can refere Manish Valecha, Dinesh Madan, or Amit Tated
DT u CAN DO IT.............Taxes are manageable..... best is Vinod Gupta.. he has satellite classes also his books are available, no need to lose hopes...u can manage it
IDT is most easy and scoring.... only one book BANGAR..
May this help u...