-Clearing CPT in first attempt is not difficult at all
-Read Accounts first: Even if it takes time make sure you understand the concepts, once you do that you wont even need a revision. You dont have to remember the very very exact detail as it is MCQ based exams.
-Than Mercantile Law:again go slow and get the concepts and you are done. You may think that Mercantile law book is thin and you should finish it quickly. On the contrary go slow and get the concepts. Bcoz this is the scoring part.
Unless you are good in maths, you should aim for 80 from the first paper (acc+merc law)
-Economics:divided in two parts -> micro and macro. micro is theory based and a few practical problems. get the fundas. the latter half of the book i.e. macro is something which you should just give a reading. As far as I remember there is not much you can learn there. Just read that portion and read it once again before the exams. Go slow in micro and go fast in macro.
-Maths:you will have to go through the book and identify areas which you find easy and prepare for them. Like some eqn based questions, statistical part etc etc.
6 months is very much sufficient. Dont worry be confident and study without tension and be relaxed.