Hello!!
I've been playing this for years and decided to dive into modding ffx3 for fun. What would help me figure this out quicker? Mainly I'm looking to add attributes/etc for now and work up to other things.
The Art docs that come wit the editor and the FFX manual are the best 2 things to use. Begin by making mult-attributes in FFX and the Art docs will help you get them in to the game.
Welcome to the community! When you're ready to make your own adventures, the EZScript manual in the "Manuals" folder in your FFX directory has lots of good info, and I offer some other mini-tutorials and examples here:
http://bentongrey.wordpress.com/2010/01/18/the-ease-of-ezscript/
http://bentongrey.wordpress.com/2010/01/21/the-anatomy-of-an-ezscript-adventure/
http://bentongrey.wordpress.com/2010/01/26/doing-more-with-ezscript/
If you have any questions that these things don't answer, feel free to ask away! You'll find that this is a really friendly community.