If you want the least amount of risk with potentially 20% gain, I'd go with bitcoins. or maybe some Ripples
I would choose Bitcoin but not ripple. I choose bitcoin because there is a huge potential that bitcoin will increase in price in the long run. If you want to choose another investment, I'd rather go for a different one, diversifying, maybe gold or other stocks in the stock market. Or if you know someone who is well verse in Forex, you can invest there too.