Once I go to the trouble of glass mounting, and putting together a show, I keep it in the trays for permant storage. Boom Box or other sound system. Extension cords, and plug strip. All this gear is expensive, but you can borrow some of it, especially the projectors. Kodak projectors are the standard.
Zoom lenses are indispensable for use in various size rooms and screens.
For large halls or gyms, where the projectors are set-up further from the screen longer format lenses would be nice, you'll pay dearly for fast long lenses. You are normally stuck with the screen available on location. A white matt screen is best in most situations where the audience is sitting to the sides of the screen. Fancy silver, lenticular screens are brighter, but do not work well for those at angles to them. Lap dissolves are less common, so you'll probably have to buy one.