As far as I know, I've been teaching students and relying on the study material provided by ICAI for CA exams especially in taxation paper is not sufficient. You can pick up a book of a good author with multi questions solved with good permutation, combinations. As per my knowledge Girish Ahuja and Singhania are good. Follow any one done mix everything together. Because following one author will get you accoustomed to kind of language and the studying will go faster and in a particular pattern.
Solve all questions from there. Also so solve last few years papers.