i think you can only earn bitcion in a fast mood only in gambling.
Gambling is the fastest way of loosing too, as you cannot expect profits every time and most of the times you will loose, so its better not to go for gambling for earning it fast.
yes there is no doubt about this that gambing is too risky and you can even lost your own money. but i have another good idea in my mind that if you hold your bitcoin you can get bitcoin very fast. because the price of bitcoin is increasing with such a high speed that you even cannot imagin.