Gambling
Playing for money is a good way for some people to improve their skills. It forces you to focus and really pay attention to what your doing. Plus, it helps to toughen up your nerves in tight situations. Nobody wants to lose money.
Another gambling option you may consider is to find a better player and ask them to play a 5-10 ahead set (obviously the higher # of sets you can get the more 'lessons' you will get for your money) for like $40. A local pro or top tier player would be ideal. To ensure they go for it, ask to play them even. Sure, you probably won't win but that's not the point. Then, down the road, when you feel your level is improving ask them again.. and so on. Eventually, they won't want to play you anymore because it will take too long to win your money. Or, you start to win their money! It's a great way to check your skill level and get some pretty 'cheap' lessons.