Can I get MBA admission at Christ University with a 680 MAT score and 91 percentile?

Yes, you are eligible for MBA admission at Christ University with a 91 percentile in MAT. The minimum required cut-off percentile for MBA admission at Christ University is 60 percentile. 

You can start preparing for the GD/PI session as the weightage of your performance during this session is quite high. You will have to go through the current affairs regarding business and management as you can be asked about any topic during the Group Discussion session. Try to put out your opinion as clearly as possible. Also, you will need to be confident and not get nervous during the personal interview. Expect to be asked tricky questions but do not lose your calm and answer the questions to the best of your ability.