What is this I'm hearing? You guys think club owners sit around an say " Man, did you see that pretty, shiny shirt that guy had on last night, or, man, that hat was the bomb! We for sure need to hire those guys again!"
Come on.....
This is music, musicians, and performing. It's not some lame, superficial, fashion show. Club and restaurant owners mostly care about the quality of the product they are paying for, not what the musicians are wearing. I refuse to play for a club so shallow that they feel the need to incorporate some kind of dress code. This is rock-n-roll man! Make a statement with what comes out of the speakers, not what cloth is covering skin.
As far as things from a 'psychological armour' standpoint goes, the psychology of the mind knowing one has done ones' best in preparing for an upcoming gig should be all one needs to feel confident and ready for the gig.
Keep in mind guys these are just my thoughts and opinions. Ultimately, comfort, both mentally and physically, is the main issue here and defining comfort varies from person to person. I do honestly feel though that the music and quality thereof is decisive in the hiring or rehiring process. Wardrobe is immaterial.
Give everything but up.