Here are some spreads of things you might need to pull off this super awesome costume
It would be easy to get a simple purple peplum dress (especially now because they are trending like crazy and are in every fast fashion store right now) and throw on a shoulder padded fun colored blazer. Don't forget the huge FLOWER in her hair and big fake eye lashes!
Here are some awesome tutorials :)
Here is Kandee Johnson's take on two looks in one. First, a doll face, and second, a Marie Antoinette look. These looks are not specific to Effie Trinket, however, the looks and techniques would definitely work for an Effie Trinket costume because Effie is very doll-like and looks very similar to Marie Antoinette!