50mbps would mean your bandwidth, and there is no such technology in South Africa...
1Gb is your Cap or ammount of data per month.
Latency is not advertised, you need to test it. (Ping yourgameserver)
I presume you still don't have the connection and is asking us if you should get this? Simple answer would be no, not unless you are not serious about gaming, there is no alternative, or you have the connection already.
The known latency issues with Iburst is not for the international leg of the data path, but it is the connection from your PC to the Tower. In this case if you cant play international games you most likely will not be able to play local ones either.