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...)
Yes you need a lot of time learning about trading, you need to lose also in order to get the answer of your own question. You also need to try it first (please use a demo account on trading to avoid money loses) to get some lessons. If he has programming skills that fit to the crypto world then that's not a problem on earning BTC there are a lot of open source project on github and he can improve some open source project there and make some money out of it. But signature campaign is the simplest way to earn BTC.