A very good way to earn some btc is to join signature campaign. Also you can start trading but you must be very careful if you do not have any experience.Whatever you do, avoid these bitcoin doubling sites you will lose your money in these scams.
Yes signature campaign are the risk free way for earning some extra bitcoins.We getting paid what we were already doing in this forum so no extra effort.Then you can try to do altcoins trading or gambling with what you earned to double them.
But yes you can also loose them in doing so.So i would be better to just hold them.