Profile review: OBC Male, Non Engineer ,10th:87.8, 12th:88, Grad:52, 3 years gap and then 6 months workex, . How much percentile should I target to get calls from IIMs and considering my profile which B schools call I can expect

Hi, Rahul.
Your profile is solid, along with 1 year of continuing work experience. Being an engineer and belonging to the OBC-NC category gives you an advantage, especially for CAT cutoffs. Aiming for a percentile of around 98 or above is recommended.
Try to maximize your score in CAT exam. You can check percentile required for all the b-schools at Cracku percentile predictor: https://cracku.in/cat-percentile-predictor
Best of Luck!