10th 95%,12th 75%,bcom 85% passed out in march2018,no work experience..CAT 77.54 percentile without any serious pre

You have an excellent academic profile and high scores in your class 10 and B Com. You are also an commerce graduate. These kind of profiles are highly in demand from IIMs and other prestigious B Schools. Since you have appeared unprepared you may not achieved the best score but if you prepare and score a good percentile you stand an excellent chance to get through to a Premier B School. I suggest you to reappear.
Prepare well. All the best!