have spent far too much time wearing academic dress so here are my personal tips (feel free to ignore at will!):
gowns come in all different lengths, but hire ones are normally either too short (hem of skirt peeks out) or too long (perfect hemline of skirt is obscured and little ankles stick out the bottom)
you can guarantee your hood will be garish. Either find out in advance what colour it'll be and get something that matches/coordinates, or go for black to match the gown.
- wear a jacket with buttons, or take safety pins
the hood usually has a loop at the front to put round one of your jacket (
not blouse) buttons to stop it slipping backwards and trying to strangle you - men have it easy as the neckband of the hood goes under a tie. Avoid necklaces for the same reason - the hood will strangle you with them.
- wear long sleeves (unless it's roasting)
gowns often have really freakish-length sleeves too, and I always find I look very odd with little bare wrists emerging from huge flapping sleeves
they have a dreadful habit of slipping off at the shoulders, making you look like weirdly risque dancer. Couple of pins may help. Some handy hints here
- keep tugging your gown forward by the front facing
the back pleats are very heavy - combined with an off-the-shoulder hood this can get both messy and uncomfortable.
- take kirbigrips if you're going to wear your mortarboard
Generally I wear a black trouser suit with a white blouse, or sometimes a camisole, as it ticks all the boxes, is comfortable, and doesn't clash too badly with my nasty yellow hood, but a black wrap dress or a pencilly skirt outfit could work too.