Which is the best site online to earn money from anywhere in the world? with a simple ad click or some little effort?
You can do something like Data Entry from upwork(odesk) or freelancer. Anyway if you got skills to offer then I suggest you use it.
You should try Upwork and Freelancer as they are tried and tested already. As far as I know they are credible freelancing sites so don't worry because you are truly secured.
If you have no skills at all, I definitely second microworkers here. Its a very simple setup and you can make money quick and easy once you figure it out. Better for USA but works for any countries.