it really depends on you, where you live and also what you are willing to do. otherwise the ideas and the businesses you can start can really be countless.
for example if you are willing to go through the hassle of starting a new bitcoin exchange service then it can be a good and profitable business in long term. but there are a lot of legal money related matters involved that needs taking care of.
also there is another common way as it was also suggested which is starting a new bitcoin casino. you can copycat others and star another dice or instead you can start being creative and start your own casino with more interesting games.