GS Tutorial:
https://www.youtube.com/watch?v=sVxO7xOYqS8
GS Demo:
https://www.youtube.com/watch?v=YTfIDJTCF70
Disclaimer: I have not used every single GS in the game and there are lots of other good ones, so don't take this as definitive or correct. I just wanted to share the top 5 that I've used so far, please leave comments on other ones you love!
First time exporting a video via FCPX so sorry if the audio is too loud, etc. it's a learning process!
Happy Hunting!
PS. Yes the Fatalis GS is awesome but it's not out at this time so I did not include it.