Right now all sort of source need capital investment. Without that making good profit is simply a hard task to be executed. In the options provided for voting I think trading and gambling gives good profit based on our skills as well we have got legitimate gambling and trading websites. HYIP's and other MLM schemes were simply a scam promotion.
For me, I see we have a good chance to make money if we will focus our time with trading, gambling is just a sort of entertainment and even if we win sometimes but it's guaranteed that we will just lose in the long run. If you haven't experience losing yet, you might be more aggressive but the moment it will hit you, you will realize you are fighting in a losing battle.
I will never recommend trading or gambling as way to tom earn bitcoin.
It's to risky really.
It's ok to trade or gamble for fun, if you have some funds to spend for this purpose, and don't care if you will win or loose.
However, if you can't afford to loose your funds, and you need it for your daily life, than please don't spend it.
It's much better than to find some free ways to earn bitcoin without risk, like collecting faucets or signature campaigns.