Crochet Hook - This little tool will save you so much time (and sanity) with all your buttons!
Friction Stick - Let's be honest, who actually likes their thighs rubbing together in a big fluffy dress? Use a friction stick (found in the shoe department or where they sell shoe inserts) and your skin can thank you later!
Tide Pen - Don't panic if you drop a little something on your dress (oh hey, red wine!) Have one of these in your clutch at your table and treat the stain as soon as you can!
Chalk - This also helps if you get makeup or something on you dress. Smooth chalk over the stain to hide for photos!
Safety Pins - I am sure your seamstress did an amazing job installing your bustle. What you can't really prepare for is when everyone is dancing the night away and someone steps on your dress! It can undo your bustle so just have some safety pins in case you need to reinforce and keep dancing the night away!!