By cutting wasteful spending, one can save money for future needs or give more to the Lord’s work. Of course, the fact that money is wasted on other things does not justify gambling. Gambling is no more or less wasteful than seeing a movie (in many cases), eating an unnecessarily expensive meal, or purchasing a worthless item.
People waste money on all sorts of activities. Gambling, if done in moderation and only on occasion, is a waste of money but not necessarily evil.