Most of the free stuff is aimed at the US players, there's a lot less for the other countries, and as you say for some there's nothing.
Have you tried doing Tapjoy offers? They are far more lucrative than any of the other options to get free credits. Some take seconds to do (e.g. download a game), but the return will be small (e.g. 17cr), then others can take a while and can have a number of rewarding checkpoints, and they can pay out many thousands of credits. If, like me, you like playing games, then Tapjoy offers are the best way to build up your credit balance. After a while you will figure out which ones to go for and which ones to leave. And make sure you start them during a 'double credits offer' weekend, which happen at least once every month. If you start them within the double offer period they will remain double offer until the time to complete the offer expires, often 60 days.