For IDT Strictly follow BANGAR'S IDT. IT'S AWESOME FOR SELF STUDY... YOU MUST REGULARLY REVISE IDT FROM VISHAL BHATTAD SIR REVISION LECTURES FROM HIS YOUTUBE CHANNEL.
FOR COSTING BEST BOOK FOR SELF STUDY IS PADHUKA AMA BOOK BY CA B. SARAVANA PRASAD SIR IT'S A WONDERFUL BOOK WHICH COVERS NUMEROUS QNS FROM STUDY MATERIAL, PRACTICE MANUAL, RTP etc...