About My Wardrobe
The most important thing to have as an EXTRA is an extensive wardrobe. The more outfits you own or can borrow, the more projects you will eligible for. As an EXTRA you will almost always be required to bring your own wardrobe. This saves the production companies lots of money and helps the casting directors decide which EXTRAS they will hire.
The best things for you to own are a tux or formal gown, three to four types of business suits, and several styles of casual wear. It is smart to have both classic and unusual colors. It's great if you have several outfits from different time periods like the 60's, 70's or 80's.
Hospital clothes, like a nurse'snurse or doctor's uniform are good as well. Alternative or unusual outfits are useful on those off the wall projects that come up from time to time. The more extensive and varied your wardrobe, the more you will work you will be ready for.
About My Equipment, props and car(s)
It is not necessary to have any type of equipment to be an EXTRA. But like the wardrobe, the more things you have the more you will work. It is a good idea to have a usable bike, roller-blades, and other sports equipment you know how to use. These can help you get work on projects that have major outdoor scenes in parks, beaches or schools. Another way to increase your job potential is to have a unique or odd colored car. Sometimes production companies don't want you as an EXTRA, but they may just want your car. If you're lucky they'll use you both and you will make even more money.