For an all itemlevel 61 geared character, you should have 570 points to divvy up among Accuracy, Alacrity, and Surge. Accuracy is obviously useless for a Sage. If you put 570 into surge, your surge value will be 80.11%. The first couple of blocks of 57 you move from Surge to Alacrity will give you almost 2% cast time reduction at the cost of only about 0.5% surge value. It does get steeper pretty quickly though, to where you're trading ~1.5% surge value for 1.5% cast time reduction when Surge = Alacrity and even worse when your alacrity is above your surge. At 570 Alacrity + 0 Surge, your cast time is reduced by 15.14% and your surge value is 51%.
It's actually 627 available points to be precise