I'm going to sew a viking costume based on either findings or paintings of east-going vikings. That is Swedish vikings or Rus. I'm looking for clothes in the period 800-1000 A.D.
Are you after male or female, well off or poor? I can provide you some sources and a lot of images and links. The subject is well researched in Sweden, but most sources are in Swedish.
Generally, if you are well off you would wear linen undergarments, woollen overgarments and cape, decorated and coloured according to your wealth. Leather shoes and woollen puttees were also common. Trousers were simple and big, knee- och footlength.
Blue, black and red were the most expensive colours. Fine fur, silk, silver and amber were common materials for decorations.
Historiska världar has a bunch of Swedish viking garments reconstructed from various archeological sources, such as grave findings, sagas, Gotlandish image stones etc.
They have pdf:s and details on each garment worn by each person, including sources.
You might need to use google translate though.