Suggestions for how women relatively easily can find a suitable costume:

Long skirts (plain/striped/chequered) 
Long apron 
Shirt
Bonnet or scarf tied at the back of your neck
Large shawl, tied at your back
Clogs

Typical colours: 
Black
Red
Green

Suggestions for how men relatively easily can find a suitable costume: 

Black pants
Suspenders
Peasant shirt
Waistcoat
Scarf around the neck 
cap/hat/straw hat/top hat
Clogs

Typical colours:
Black
Red
Green