Hey,

CAT isn't as such a very tough exams and can be conquered with self study if given good amount of time and hard work. If you give an intensive amount of time with proper strategy for like 5-6 months, it would be more than enough for you to crack that exam. But if still want to continue it with some good institute then it may also work for you. You can go for TIME, CAREER LAUNCHER, ALCHEMIST, IMS and more. These are some good coaching institution for MBA with great study materials and test series.

Hope this helps.