Does someone has any suggestions how to make 17 BTC with 7 BTC starting capital in short period of time?
I think that you can try to gamble with them because that can earn you some quick Bitcoin but the chance of winning is not big so now what can happen if it goes wrong.
If you do not want to do that then you would have to use your own money.
Gambling is such a risky factor among any kind of investment in the bitcoin. Just put into trading and make profit or else put into your cold storage or paper wallet and wait for your bitcoin to reach the good value.