There is no fixed or guaranteed way to make 17btc form 7btc.You can try different things like gambling or trading but in this way you can also loosed the 7 btc amount and if u dont want to risk then I dont think there is any way.
Taking risks is not bad but not risks like gambling or ponzi schemes and hyips, but risks like trading is good to be taken on the condition of having enough knowledge about it, if someone having no knowledge at all takes the risk of trading then he would surely lose his capital.
The trading is quite risky. I have lost most of capital due to trading the altcoins. The right timing is difficult.