How much money do I need to save for a trip to Miami ?

My two best friends and I are planning a trip to Miami , FL in July . Keep in my that we all are 18 so of course there will be plenty of partying . Now yes we all like to shop , especially me but we're smart shoppers . I estimated about $300 . That's for the hotel , going out to eat , shopping , parties , etc . I assume that may not be enough so help me out people !