I'd say a majority of people attending cons are cosplaying one way or another, so don't worry about that (:
What I do when I begin a costume is make a list of absolutely everything I need, and I check it off as I go along. It really helps with organization and that way you don't forget anything.
Next, you should set a budget, you'd be surprised what kind of deals you can find.
I also really like to look at other people's take on the same costume, to help me plan and sometimes they have information on how they made and where they bought things.
I hope this helps!
Maka Albarn; Soul Eater
Anarchy Stocking; P&SwG
Imp Midna; LoZ Twilight Princess
Megpoid Gumi; Vocaloid
Medli; Legend of Zelda Wind Waker
Goddess Madoka; Puella Magi Madoka Magica
Sasha Brauss; Shingeki no Kyojin
Originally Posted by sam vimes
Kōhai. Her name is now Kōhai.