What is the best resource for Learning LUA?

An excellent resource for programming is lua.org. Also there are many resources on Amazon( although not free) for a small price that give you a complete and user-friendly guide to learning LUA. Also a good source for ROBLOX is this site actually. You can search for things you need but try to keep your search short so you can get more results.

Example: change " How can I sort data" to: "sort data " or "sort keys" or "sort items"

Try different words and see if those work.