Not at all! It is definitely fun to wear a costume to a cosplay convention, but it isn't required. There are a lot of people that go in their every day clothes just to appreciate other's cosplays, meet people with similar interests, and attend the panels.
You can wear anything you'd like. If you can't buy a Cosplay costume make your own costume with whatever you have and try to make it look similar to a Anime TV show you like.
Go to an online store, find the costume, buy it, wear it. ^_^
Buy the costume.
Are you going to a anime convention? You don't need to cosplay. It's not a must... unless there is a rule for that particular convention.You could just wear a wig and a cute outfit, and say that the character you cosplay would wear this too. Or just wear something similar. You don't have to look exactly like that character.
Just about every Japanese pop culture or anime manga convention is a cosplay convention.
Google Directory Cosplay http://www.google.com/Top/Arts/Animation/Anime/Fandom/Cosplay/ Anime Costume resources: http://anime.about.com/od/cosplay/tp/aa12.htm
Cosplay Station (dot) ca will make them on commission, but they are very expensive, around $225.000. You might be able to find a dealer at a CosPlay convention who has them, or do an internet search. Most people make their own costumes.
you can buy a cosplay costume online or you can make a costume yourself. There are also many places where you and other people can cosplay known as cosplay events.
This is what I found, you can have a try on cosplayshow.com a good website for cosplay costumes
From Kingdom Hearts? Go to the cosplay store in the links. Do a search for the costume or ask them to make it custom.
Well if it's just for cosplay you can buy it on a cosplay website (full costume)
Cosplay (short for Costume Play) is dressing up as a specific character, usually Anime characters.