For me I do prefer to use the investment and trading if I wanted my money to get double. Investment is pretty good when it comes on gaining a profit however it will takes time in order for you money to get double. Next is trading, I chose trading because I also earning in this way and I guess it is effective however it requires a experience and knowledge about bitcoin since trading is a tough job. Regarding on cloud mining I never been try it before so I can't tell if there's a possibility for you to gain profit here.