I think that it is the only major leading source from where we can actually earn bitcoin
but i am not sure about trading
Gambling is something to avoid , trading could definitely be profitable If you know what you are doing but before starting to earn , you will probably lose the time you start learning lessons about it. Basically , you can do whatever you do to earn fiat to earn BTC , offering services on the forums is probably the easiest thing to do at this point but require some skills (web/app development , design etc...)