Start by search for stores like Bodyline(Japan) which are located in Harajuku. Interact in forums dedicated to cosplay for reviews and tips on the best shops offline and online.
You could order gothic clothes on the computer.
when you go shopping you can say that you can pay for your own clothes and get gothic clothes little by little un til you have the amount of gothic clothes you want.
Bookstores....gothic stores....some video game stores carry them. If all eles fails, go online and order them.
gothic stores maybe like spencers, just go to the mall
Anywhere. Goth things can be found at any store if you look really hard at stores that aren't entirely preppy.
princess tutu D.Gray Man Witch Hunter Robin
russia
i don't know about anime but you can buy manga at timemasters inc. or even chapters and you could order anime trough chapters.hope this helps.
Hot Topic is a good place
You can Buy them Online or at Anime conventions.. the anime Convention i wen to i got a Miku Hatsune Plush
You can get licensed anime in a lot of places. I use Amazon.
Princess Mononoke .