Hello, Tom... and welcome!
First thing you'll want to figure out is which costume you'd like to do. There are literally hundreds to choose from. You can make your own stuff or buy the pieces and parts. We can help steer you in the right direction(s) of the best place to buy items if you go that route. Whatever you end up with, you want to enjoy it and be happy with it... so pick what makes you happy!
Here is a directory of currently approvable costumes. It explains each part and piece, and know that a costume must get approved on you... so although there are sites that may sell a costume "complete" as 501st approvable, remember, it has to look right on you and there is not off the rack approvable costume. Now, that's not to say it can't be... just know it's not a 100% guarantee.
https://databank.501st.com/databank/Costuming:CRL
The Carolina Garrison consists of North and South Carolina. The 501st is broken up into Garrison, worldwide, just to help with events being able to be posted on event calendars in specific areas. Once a member, you can troop anywhere in the world.
The 501st also has detachments. These detachments are groups of like costumes. There are about a dozen detachments... Sith Lords for... Sith Lords... Imperial Gunner Corps for Gunners and costumes with the gunner helmet. Bounty Hunters Guild for all things Bounty Hunter. You get the idea
Again, once you have a costume in mind, let us know and we can point you in the right direction. Once you get a costume, and get it to the point where it looks like you're ready to submit for approval pictures, you'll be well on your way to becoming a member and getting full access to the website, which will allow you to see all events in the Carolinas.
Hope this helps
Thanks,
Chris