No ingredients

Hello, I'm a college student and I live alone. I normally cook only for myself. After making several bento boxes, I realize that since bento is like having a little bit of this and a little bit of that, I need to stock up many ingredients in my fridge. Items like eggs pose no problems, but the problem comes when I need vegetables. I can't buy just a tiny piece of vegetables from groceries store, so normally I end up with rotten vegetables in my fridge because I can't make use of them before they go bad. Do you have any suggestions on what items I can store in the fridge for quite a long time before they go bad?