Anything other than signature campaigns and gambling.
A bit saved is a bit earned. So save your money by not clicking on any of the signatures of the people posting in this thread.
just common advise

anyway gambling is just worth of luck and its up to the user how he/she will use her bitcoins. Still be wise on using it.
Yes, gambling is just about your luck

If you have great skills then for sure you can render services and post some of your skills, make some freelance job there were bitcoin payers. And if possible avoid gambling.
You're right. It is best to avoid gambling. They can not lead to anything good. I myself was fond of it once. Then I realized that I would not earn anything.