From all this answers I see we can choose between ponzi schemes, gambling, trading. But more or less everything of this things is a gambling, so maybe its best thing to try it. Find some good strategy, or you can check google for some tutorials and sites offering some winning strategies.
i think if we know about investment in gambling, its a good investment but you still be careful when you want to make any investment. for me, i am lending some amount of bitcoin into market exchange and i think i am making some of bitcoin and i can see its really grow although its not a big amount.