I went through the introductory lecture and understood that Sec C cover all other sections except costing techniques. My doubt is do we need to prepare for costing descriptive part Sec C? Or is it enough to get prepared for Sec A &B both description and numericals? Please advice.
Costing techniques (both calculations and descriptive) can be asked in Section C but if they are (which is very unlikely) they will only ever be a very small part of the question.
I assume that you have a Revision Kit from one of the ACCA approved publishers (and it is vital that you do have) then you will be able to have plenty of practice at all the topics that can be asked in all three sections.