I suppose I'll weigh in-
First things first get yourself a TK, a WHITE ONE! Power in numbers baby, you can wear it to any troop and be loved. Plus there's nothing quite as cool as when a bunch of white troopers are together.
Next get yourself your favorite character, EU, Rebel or whatever, this is the character that you'll have the most fun costuming as, and you'll want to take a break from armor pinches here and there.
Then get a character that is recognizable yet unique. Good examples are the clone commanders, I know half the kids don't know or care who Commander Bly is but they know he's a Star Wars character. or do a random Mandelorian, people may ask you "Which Fett are you supposed to be?" But forget them... Mando's are cool. just don't do a 181st TI, cuz that's what I'm working on next.
Lastly, GET SOMETHING HUGE... the bigger the costume the more love you get - Chewie and Vader always have a crowd of people around them. Biggie Size yourself and feel the love
I also believe that everyone needs to have an Officer's Outfit, it's a good back up in case some crazed Red Belt kicks your hip out.
Unless you don't mind being called Darth What's His Name, Willyfae, Skeletor, or Death Eater #23 don't be Darth Nihilus
Unless you're having a Star Wars themed wedding or something, don't do a Jedi costume... Jedi's are stupid