As the institute is below average, but there have been students from RGUKT who have cracked the CAT exam in the past. CAT is considered one of the grinding MBA entrances. There were around 75 alumni who sailed through CAT. Most of them had percentiles that were above 98 and got admission in top B-schools like IIM A, B, C, K, and more. 

You can prepare for the CAT from the last year of your engineering degree. You need to understand the syllabus and practice solving the past papers. Many academies, like Kish Academy, conduct seminars about CAT. They give insights about how to prepare and what it takes to clear the exam. 

For the dream institute, IIM A, you need to score 99.9+ to get a call as an engineer. Even after receiving the call for an interview, you should ace the interview round. 

If you are prepared and well-practiced, you will be able to score excellent percentile. You do not have to fear the institute from where you completed your graduation.