My partner sews and she started with a "maternity" pattern for overalls. You add contrasting ruffles and pockets, plenty of bright "piping" in all of the seems. Large buttons, etc. She then took a solid color long-sleeve t-shirt that matched her colors. Added a matching collar and bow and matching cuffs! Beautiful costume!
Don't forget LINING is your friend! It may seem like it would make it heavier, but it actually makes it cooler and the costume lasts longer. Looks crisper. It actually keeps the costume from sticking to you in the heat as well.
Good luck!
Sparky
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