The ISB would like to admit well-rounded students. Extra-curricular activities add that extra dimension to your personality. In the US it is routine for people to do community service, which they can mention as an extra-curricular activity in their applications. But Indian conditions are different, so not having done such activities is understandable. However, if you look deep down, you may find some things that you may have been doing. Did you tutor a kid anytime, did you organize a festival in your apartment complex, did you volunteer your time in some campaign or raise funds for some cause, etc.? If you haven't done anything at all, it's never too late to start. Don't do it just to get your B-school admission, but do what interests you. If you are in the IT area, think of something related to IT that you can do after office hours. How about persuading your company to donate their obsolete computers to charity? The possibilities are endless.
To have a successful career its very important to understand your preferences and chalk out what you want to do with your work life — nature of work, kinds of companies, broad location preference and your own aptitude. If you have all this clear chances are this will reflect in your application essays. Ofcourse focus on grads and GMAT is important as well(simply because there are alot of good people out there and certain parameters are needed for comarison), but there are several cases of “My GMAT and acads were better than his but he got an admit and i didnt”..and frankly the difference is the maturity and clarity in application essays that can be a clincher. Its a bit of a mirage and never a complete perfect answer but the more thought and experience you put into your planning the better its reflection will be. A strong application will sail through irrespective of R1 or R2.