Clothes Do Not Make the Man
(a person should not be judged by the clothes he or she wears)
I saw Howard the other day in a costume store. He was renting a suit of armor for a costume ball. Sally's going to be there, and he thinks she might agree to go out with him if he projects a more manly image.
He must be dreaming! Doesn't he know that clothes do not make the man?
He's convinced that Sally has always refused his invitations because of his puny appearance. Evidently he doesn't realize that she's not going to judge his character by observing the clothes he's wearing.
You said it! A suit of armor won't change his appearance or his personality. Still, I wish him luck.
costume store = 貸し衣装屋
go out with = （異性）と付き合う
project = 演出する
be convinced that 〜 = 〜と信じている