I do three of them.

Invest- just hold my coins and wait for it to reach my target price. If I think the price is cheap because of price decline i buy more to increase potential profits.

Trade- doing okay at this area. My capital is small but at leat i am not losing money.

Bounty- obviously i do this just look at my signature.

Which i think is best way to earn money.
Investing- why? Because after you buy you can forget about it. It does not consume time and effort.
Trade is the most profitable if you know what you are doing.

Bounty/sig campaign  is just a little extra money, it will not make you rich but you can help the project and they can help you by them giving you a few coins.