For accommodations, I recommend booking early so that you hop on a quick and good deal. If you can get a good airbnb, great because you can get groceries and eat some meals at home. Greek ingredients are so amazing that you can always make an amazing Greek salad at home that is just as good as the ones you get in the restaurants. I suggest that you only spend money on food and going out clubbing. You can find small and public beaches where you don't have to pay for a beach chair.