You should always wear casual clothing and comfortable walking shoes to the parades. Many times your shoes will be stepped on so you do not want to wear anything you wouldn't want ruined. You may also have to park a distance from the parade route, so you'll want to be comfortable. You should bring a large bag to collect your trinkets and throws in. Admission to the traditional balls held is by invitation only.
Most invitations are non-transferable.
My neighbor is bringing a ladder. Many people bring ladders to parades for height advantage. Some even build custom ladders to seat children in them. The legal alcohol purchasing age is 21.