Hi Patricia! This is always a question even the seasoned Disney traveler asks for each trip to Walt Disney World.
There are many things to consider and the first is weather. Check the ten day forecast for your vacation to see what the highs and lows will be for the days and nights. Bring light sweaters or jackets For morning and evening wraps. If you don't do this you will end up with a closet of Mickey sweatshirts you have to buy in the parks to stay warm.
Also check for rain possibility. Rain is not uncommon to central Florida and you can see a shower each day in the summer months. Bring raincoats or umbrellas or plan on purchasing a rain poncho in the park if the need happens. Definitely pack at least two pair of shoes as well. You will not want to wear wet shoes if you don't have to as they will cause blisters quickly.
Now speaking of shoes you will want to select only those that are comfortable and supportive. You will be walking far more then you do at home and you will want to treat your feet to every comfort possible. Sneakers are great unless they get wet but there are many other brands out there that offer comfort sole or air foam which will be good. Please don't worry about being fashionable when you are traveling to Disney.
Dress is casual just about everywhere. Some of the signature restaurants offer you a chance to dress up a little but only Victoria and Alberts require jackets for the men. Park attire is the norm in almost all restaurants and again remember to bring a wrap as the air conditioning can be quite cool.
Consider a small handbag or backpack for the parks but please don't try to bring everything you own. You will be uncomfortable carrying a heavy bag and dealing with it when you are on attractions is not fun. Also, check out the list of things that you should not bring into the parks
HERE.