Hello, tsangwailam, and thank you for using the SEG.
I am one of the maintainers of the Graphics Extension, and unfortunately I do not have a lot of time (End crunch on game project right now) to put together a Wiki or a description on a lot of use cases for the project. It's a great idea, but I do not have the time right now.
But, I will be happy to try to help you out in here.
It is hard to give any specific tips for making the Graphics Extension run faster, but in general, the tip will be: Do less each frame
For example, are you re-creating a lot of geometry for every frame? Can you give me some sample code that you think ought to run fast but doesn't?
Quite a bit of work has gone into making the SEG as fast as possible, but since we are competing with the native Flash Graphics API, which runs mainly in compiled C code, on the "inside" of Flash, there's always going to be a losing battle trying to make things that run fast in the regular Flash API run equally fast in Starling.
That being said, there is usually plenty of things that can be done to speed up performance. If you have a specific scenario, or a small test harness with code, that you could put in here, I'd be happy to help you out, if I can.
Does that sound fair?