It may seem like your acquisitive cousin never talks about anything but shopping. Someone who's acquisitive is preoccupied with possessing material things.
If you were trying to improve yourself by becoming less acquisitive, you might destroy your credit cards and force yourself to take a break from buying things. The adjective acquisitive comes from Latin word for "accumulate," acquirere, so when you're consumed with accumulating more and more, you can describe yourself as acquisitive. It's an easy word to confuse with inquisitive, which means "curious or inquiring." It's much better to be inquisitive than acquisitive!