~ sprigged dress 
   or pastel dress
   or two-piece blouse & skirt outfit (two colors--blouse might be white)
~ ankle length or mid-calf
~ bonnet? mobcap? ribbon?
    (headwear depends on character)
~ Mary-Jane type shoes usually work;
    some types of sandals might look right
~ knee socks or tights (often white)
~ add appropriate props: ie.
Bo-Peep = staff 
(cane with ribbon-bow)
Miss Muffet = bowl/spoon/plastic spider
Jill = carry pail
Mary Contrary = basket of artificial flowers
Mary who lost lamb = books or bookbag; toy lamb attached to belt
 
 

~ usually short pants - dark color
  (use summer shorts)
   or knickers (cut long pants below knee 
   and gather with hemmed elastic
~ dress shirt with or without bowtie
    or striped tee shirt
    (depends on character)
~ hat? soft cap? (depends on character)
    (baseball cap is too contemporary)
~ solid-looking shoes or boots;
    possibly some brown sandals
    (no tennis or other sport shoes!)
~ dark knee socks are often seen
~ add appropriate props: ie. 
Boy Blue = horn
Jack-Be-Nimble = candlestick
Tom, Piper's Son = flute
Jack Horner = artificial pie
Jack = pail
 
 

The main thing to keep in mind in creating a costume is that it should be colorful and that the outfit should convey some sense of the old-fashioned that children expect, based on nursery-rhyme illustrations they've seen. 

Basics of a Mother Goose Costume
Main outfit possibilities: t
~ the skirt should be either ankle or floor length 
            (ankle-length is easier to walk in) 
~ print or gingham skirt with bright top 
~ print or gingham top with bright skirt 
~ long, print, old-fashioned-looking dress (muu-muu?
~ long "at-home" gown?, etc.
Important accessories: 
~ add an apron 
~ add a shawl or scarf at the neck 
Head cover:
Mother Goose's head is usually covered with something 
~ a tall black hat (like a witch's) available at a costume shop, or widely available at Halloween; add some colorful ribbons and/or artificial flowers 
~ straw hat decorated with ribbons and/or artificial flowers 
~ bonnet 
~ mob[-cap
~ seen on one Mother Goose: an ornamented nurse's cap 
Legwear: consider colored tights, leg warmers, or knee socks 
      (though the long skirt allows somewhat more leeway) 
Footwear: 
Leave your high heels at home 
~ boots look Mother Goosey 
~ walking shoes can be made to look spritely with colorful laces 
~ sport shoes are available in a colorful patchwork pattern 
Jewelry:
Try to avoid contemporary-looking jewelry (rather go with none). 
~ craft stores have "findings" (links, earring clips; etc.); all you'll need is strong tweezers or pliers; look for plain baubles, or for charms of a goose, star, sun, world-globe, etc.--anything you think applies to Mother Goose
~ consider having each earring different 
~ if you are familiar with computer clip-art, you might even make "Mother Goose" jewelry (or cajole a friend); print out whatever size you want to make; give it body with clear press-on film; cut out the designs and attach to findings; designs to look for: Mother Goose, goose, Humpty Dumpty, etc. 
~ plain colorful bracelets are okay 
~If you're just going to parade, you might carry a basket. However, that gets in the way if you're going to interact with kids (unless you're carrying goodies to distribute) 

Use your common sense. 
dress colorfully, preferably in a print 
don't forget the apron, shawl, head cover, and appropriate-looking shoes 

Any Mother Goose should 
~ be warm and friendly 
~ smile 
~ have fun herself.