If you are really eager to some items, I suggest you just search them online. There are many sites you can trust like mycosplayclub.com.
The cheapest way to go is to find a character that you A) already share a majority of features with and B) doesn't wear a lot of unusually costume pieces but does have a unique appearance. It would help knowing what you look like to better answer the question as well as what kind of costume party it is...
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.