Here are some awesome resources across the web for learning:

http://www.footbag.org/ - your one stop shop for intro all the way to pro

https://www.passbackfootbag.com/home - great trick dictionary, and retail shoe

http://blurryworld.com/foot-pop/ - fun game and a great way to visualize tricks!

https://www.reddit.com/r/footbag/ - reddit community