I figured out that playing Galactic War(minigame) you can get 1000 points in 105 seconds. For every 1000 pts you get 1 SG.
1 minute = 60 seconds.
1 hours = 60 minutes
60(s)x60(m) = 3600 seconds.
This means that you need to play almost 10 hours or 31500 seconds to be exactly, in order to get 3.000.0000 points that equals 3.000 SG.
Pretty amazing, right?