You're going at this all wrong.
I used to teach folks at your level, up to 3'3". Wanna know what impresses me? NOT clothing, or tack or fabricated questions.
*Be early
*Be attentive
*Be polite
*Use proper ring etiquette
*Ask intelligent questions based upon the exercise I'm putting you through.
*If you do not know something, don't act like you do -- be HUMBLE
*Don't ride above your ability or overstate what you've done
In regards to your concerns, dress properly for your sport, ie: low heeled boots, like paddock boots, a collared short that's tucked in, riding breeches & a belt with black half chaps or tall boots, gloves. And ASTM approved helmet, too, of course.
Far as tack goes, I don't care of you ride in a Butet or a Stuben, in a Jimmy's bridle or a State Line Tack special. All I care is that it FITS, is in safe condition, relatively clean, and appropriate for the job. Don't show up with your horse in a gag if you're only jumping 3'.. there's absolutely no need for it.
Most good trainers are way too old & cynical to be 'impressed' by any new student.
Ride well, be normal, have fun.