Which is the best college to choose for a student who got 18000 ranking in kcet?

You can use the KCET college predictor to find out which colleges you will get based on last year ranks in the same range: https://www.shiksha.com/kcet-college-predictor

Your rank is not supporting you so much. Best for you would be to check some good colleges and take admission the basis of your 12th score. Check for the academic benefits you can get in the form of scholarships, faculty, exposure, platform etc. Log in to some good college sites to check the cut off