Angels: A white T shirt with gold net attached to the bottom (can be worn with leggings), a large pillowcase with holes cut for head and arms, tinsel halos, home made angel wings
Shepherds, Mary, Joseph, Innkeeper:
Tea towels and headbands (5 for £1 from the Pound shop!)
An oversize/ adult T shirt decorated with marker pen stripes
A length of off cut material with a head hole cut out of the middle (can be worn as a tunic with a belt over trousers and T shirt)
Wise Men: Any of the above with cloaks made from pillowcases/ lengths of fabric fastened with safety pins or badges, cardboard hats and crowns
And if all else fails dressing gowns are very useful!!