You only get Void Points if you have the appropriate feat. (using the Void Points rules from the Rokugan hardcover)
The Void Use feat gives you 2 void points, and allows you to use them as per the rules in that feat.
Non-humans and characters not native to Rokugan may not select this feat, except for Naga characters, but they call it Akasha Use, and it provides Akasha Points instead of Void Points.
The Depths of the Void feat provides the character with 2 extra void points, and can be taken multiple times.
I BELIEVE it got errata'd SOMEWHERE that Depths of the Void grants 3 extra points, but I'm not sure. We play it with +3 points instead of +2.
And no, your points don't change based on ability scores, levels and so on, only based on the feats.