Ivy league colleges don’t want anything different from other colleges. They want to some insight into what sort of a person you are. You want to come off as the sort of person someone would like to have as a roommate and who would be an asset in class. There’s not one magic formula. You can be a quiet introvert who thinks deeply, a wild extrovert who gets lots done, have a quiet sense of humor, be passionate about some particular intellectual field, or any number of other things. Many colleges also post essays they liked on line. Here’s the Tufts one https://admissions.tufts.edu/apply/advice/past-essays/