The Roblox Wiki is one of the best ways to learn how to script but unfortunately, all of the tutorials on there have been scrambled due to the redesign so this guide is just sorting out the tutorials again so you can read them in the correct order. This guide should cover everything you need to become competent or at least confident with Roblox Lua.
This will not guarantee that you will learn Lua quickly or even at all. It's your responsibility to use the resources here effectively by taking your time, taking notes, practicing, etc. This list will be updated as I find articles on important concepts that I overlooked so make sure you check back frequently.