Resource Page: Latin: Lingua Latina Per Se Illustrata
I've said it before and I'll say it again- this is the single best introductory language textbook I've ever seen.I implore all learners of Latin to go out right now and read this!
Disclosure: Some of the links in these pages are affiliate links, which means I will get a small commission for each purchase at no additional cost to the reader. In every case, I have either used, regretted not using, or plan to use the products on the site that I recommend.

LLPSI:
Familia Romana
This is the main textbook you'll need for the course. You don't actually need any more, but the other two will help.
Note- The textbook is entirely in Latin, so you can buy any version you wish. They're all the same.

LLPSI:
A College Companion
An excellent companion to the main textbook which might help you get even more out of your Lingua Latina. Not written by Orberg himself.

Colloquia Personarum
An excellent reader that supplements the first 25 lessons in LLPSI. Definitely recommended.