I am a GEM(General, Male, Engineer), with 9.8 CGPA, 83%, and 7.2 CGPA for 10th, 12th and Grad. What percentile would be good enough for IIM Calls?

It depends on which IIMs you wanna get into. If it is old IIMs then you need a percentile around 98-99. Not so old IIMs like I and K a percetile about 97. And for baby IIMs you need a percetile nearer to 95. If you have an EWS reservation then the percentiles will be around 97, 95 and >90 respectively(given that you have cleared all the cutoffs). I think it would be better if you aim for a good score than a good percentile(since percentiles may vary a lot depending on the difficulty level of the paper). But scores give a better picture. Whatever the difficulty level, a score about 160-170+ , 140+ and 110+ will be good to get you calls from old , not so ols and new IIMs respectively.