Comfortable shoes are the number one most important thing for walking a convention floor. Not only will you probably be walking from the shuttle stop/your hotel to the convention center, but you're going to be spending HOURS on your feet on oftentimes horribly uncomfortable concrete floors. As I am a serial "giant stompy heels" wearer, I sometimes don't take my own advice - and regret it terribly as I lose all feeling in my pinky toe for two weeks straight (yay nerve damage!). I usually save my heels wearing for the after parties or dinners, and stick to trendy yet comfortable shoes for the convention floor. I've found things with big soles really help absorb the pain of being on your feet for 8+ hours.
Airy, Moveable Dresses
My go to Convention uniform is usually a dress, comfortable shoes, and a cardigan or light jacket (not anything too heavy, so I can carry it in my bag if I get overheated). I'm not a pants wearer, but I also at times enjoy just a simple long tanktop with some geeky leggings. I like airy, comfortable clothes for geeking out all day in. Above are some of my favorite dress picks!
A Big Huge Bag
A big huge bag that is comfortable to wear is absolutely CRUCIAL (further down I'll add a bonus checklist of the Convention bag essentials!). Not only do you need your "essentials", you also need something to throw all of the stuff you buy into. I prefer to just have one big bag that does all the work rather than carrying around a bunch from the Vendors (though We Love Fine DOES have the cutest bags ever). I like a big huge side sling purse as it's easily accessible, but a backpack with big straps is also a viable option.
These are THE ESSENTIALS - make sure to always have these with you at a convention! Convention Center food is always ridiculously overpriced ($10 Nachos?! NO THANKS!) so I always carry snacks and water with me. Painkillers, deodorant, travel perfume, lipstick, and concealer also never leave my bag... and of course a camera, sharpies (for getting/giving autographs), and BUSINESS CARDS (cons are the best place to Network EVER!).
What about you guys? What are your convention essentials?