I don't have a million dollars to be spending on brand name vintage clothing so I opt for the more reasonable approach and buy clothing from second hand stores, flea markets and antique stores. Sometimes the clothing you find may not be in tip top shape and some sewing skills may come in handy. Also the clothing does not have to be a true vintage clothing item, it can just look the part.
I especially love the hair and makeup portion of the look it just ties it all together. If you would like to do research on the particular eras hairstyles and makeup there are many websites that specialize in hair and makeup of a certain era. ( I will list some below.)
Victorian and Edwardian- gibsonglamor.blogspot.com
1920's - 1950's- www.vintagehair.com
makeup and fashion 1900's- 1960's- glamourdaze.com

Images from google.