Hey you can start with "ISCA"
Also start preparing your notes point wise answers. It will help you to revise for 3 to 4 times before your exams. Last minute revision.
Togather with ISCA, take Costing.
Hit on Target costing, Transfer Pricing. There is a sure shot from this chapter. It's a small chapter and you will have the benefit of leverage.
Also, concentrate on theory of costing. It carries 20-25 marks.
Last but not the least, Marginal and Decession making is most important.
Also, O.R. you may refer study material.
All the Best and have a happy reading.