Dude, firstly.... no sir business. im a first year doing my btech -_-
Secondly, what you have to do depends on what confidence level you are at. Do you think u can crack mains easily? What is your main aim? IIT? What is your backup? Do you think that you can easily clear the entrance for your backup college+branch?
I had clear cut answers to all of the above questions. Frame answers for these first.
Assuming that your end goal is getting into an IIT, and If you think that you can clear your backup easily, give 30% of your time towards the backup and 70% to your main aim(slowly decrease this ratio as the date of the exam approaches). If you dont think you can achieve your backup, its time that you drop everything and put all your energy into clearing that first.