I'm currently on Hotlink prepaid broadband, I buy the 25RM 2GB for 10days subscription and it's more than enough for me. I even play a few games with my brother and cousins.

(Hotlink does have a 68RM 4GB for 30days prepaid subscription, but I get more by buying 3 successive 25RM subscriptions over the 30 days so I could get 6GB in cap total. And yeh, I do use up 2GB every 10 days easy--Jaedong's stream is still cool at 360p).

Downloading the current ladder maps won't take more than 10MB in total, and a game of SC2 shouldn't even be more than 1MB. That shouldn't take too much of a hit on your cap.

What sucks though is the unreliability of the wireless signal. An Edge signal is unplayable. And the times that I do get an HSDPA+ signal, I still get lagspikes every couple of minutes or so.