Make sure you also verify with your assignor that you're purchasing the correct uniform. Some want navy pants, some want grey pants, etc, etc, etc. Before you spend a couple hundred dollars on equipment, make a phone call first.
Also, find out if some of the more experienced umps in your organization are selling any of their equipment. That's a good way to save a few bucks on chest protectors, leg guards, masks, etc., until you can earn some cash from calling games.
Lastly, definitely visit this board often. We're a spirited bunch, and there's more experience here than you can shake a stick at. If you ever have a question, someone here will have the answer.
Welcome to the blue, IHSARef!