Gambling is not an investment or a method to earn BTC imo since it's just random playing and can result in losses as well as profits and not like trading with an edge but the opposite with an edge against the player... Get paid to sites are profitable if you are in the US but faucets are rarely giving any decent profit.
Gambling is surely not an place to earn bitcoins but its a place to loose bitcoins and it is the most risky way to depend on earning bitcoins, if you are a safe player then best choice for you is signature campaign.
I agree gambling is not the place if you want to earn bitcoin, it is the place if you want to gamble bitcoin
. Anyway if you want to earn Bitcoin in a more safer way, you can equip yourself with skills about internet marketing, or designs, or bbcoding and offer your services in the internet. People will more likely buy your service if they see you are good enough for the job.