Chartered Accountant

First of the all, basic maths is needed each and everywhere in life. And when coming to advanced maths like integration and all. They are mostly useful in CPT and somewhat in final. Being strong at maths is surely going to help you in costing and financial management as well as accounts.
Maths may not be as much needed when you pursue your CA course but once when you are done with CA and you want to join some field like investment banking, stock market, portfolio manager, financial analyst, etc., you will understand the dire importance of advanced maths. Many leave up maths in CPT thinking that the other subjects will set off it.
One thing I want to say to each and everyone pursuing CA, please do not study just to pass, do not mug up the concepts, understand them and practically apply them in life. You might fail once or twice in the exam (chances of which are also very less due to concepts being crystal clear), but you will never fail when you go out there in the cut-throat competitive world.
So, yes maths too is important, not that much but yes, it is.

Accounts:
This is the most scoring subject in CPT , no doubt. It is very much required that you must solve all the mcq sets given in the module. Please don't leave the company accounts part. A lot of students get irritated and leave it for option. It is a crucial part. In CA-IPCC a lot of concepts are on shares and just company's fund management. Once, you are done with the entire syllabus of accounts , move on to solving past year papers as much as you can (I am not referring to the model test papers module in anyway, it's straight up of no use). Redoing the syllabus again and again isn't gonna help. You must practice and develop the much needed logical approach. Not every question is going to be direct. If you get the flow of the exam oriented questions , you are good to go. :) I will link the past exam papers at the end of the answer.
Mercantile Law :
There are three acts. Out of them , Indian Contract Act and Sale Of Goods Act are important ones. I remember revising law for almost 10 times before the exam. Every detail in the act needs to be taken care of. If you are not clear on any interpretation please get it cleared the very next moment. Ignoring small things can cause disaster. ICAI has a knack for asking questions on minute details which a lot seem to ignore. Also, if you are planning to refer coaching notes or any other reference books. Then, give few readings for coaching book but reference books are not needed at CPT level. The institute's module is a must to be covered.
I remember solving a set of 600 mcqs for law just 3 days before my CA-CPT exam. I had to be sure enough that nothing remains unattended. I kept practicing. Law , looks really easy but it's twisted. Why I am emphasizing so much on the interpretation is because a small word in the question can change the entire meaning of the question ! You need to be very careful with reading the questions as well.
Maths :
The most hated subject for CPT level. :P Don't study from ICAI's maths module , it's way too lengthy and will confuse you unnecessarily. Yes, but do solve those sets of mcqs from module. They are really good and challenging. I cannot offer much help here since I was really weak at Maths. I studied from my class notes and practiced from ICAI's module for MCQs.
Economics:
Same as Law but for statistics part, I would recommend you record your audio while reading out loud the stats and play it again and again whenever you get time to.