Hashocean until they close. 
That's just speculation.
It has not been proven nor disproven that they are a ponzi.
They may be aponzi so you may be riht that they will eventually close, however, they are still one of the best investment ideas and have been going for nearly a year with sustainable profits.
The best investment option involving Bitcoin is.... Bitcoin itself. Bitcoin was originally intended to be a currency. But nowadays, it is mostly behaving as an investment asset. And I would advice every one to stay out of the other Bitcoin-linked investment options, such as crypto-stocks. Most of these schemes are ponzis, run by conmen.
I agree! Buy or earn some bitcoin and wait for the price to rise and sell them for profit. I would like to advise that you will have to invest only the amount you can afford to risk or lose. Bitcoin price goes up and at the same time it also goes down.
That is hard to do and requires lots of time from an invesstment. Whereas, other investment options usch as cloud mining are much faster but have greater risks.