Photobooths and event setups have their own weird little ecosystem of gear. The things that save you are rarely glamorous: washable table coverings, signs guests can actually read, clamps, labels, tape, and props cheap enough that you will not have a crisis when somebody spills something on them.
Cheap, replaceable tablecloth for photobooth props

Personally used: I use this on my props table at events. The price is low enough that I am comfortable buying ivory and lighter colors knowing they can be washed or simply replaced when someone inevitably spills something—or an ambitious child finds a Sharpie while I run off to photograph the dancing.
Custom message lightbox

I have customized versions with my company logo and love them. At home or in a studio, you can keep an encouraging message visible. At an event, it becomes easy signage for a photobooth prop table or other guest-facing setup. As a gift, I especially like the idea of setting the recipient’s message before wrapping it.
Changeable letter-board sign

Friend-tested: my best friend owns one and I have changed the letters with her many times. It takes forever, but the result looks classy enough for weddings and formal events. Think prop-table labels, welcome messages, or “no phones during the ceremony” signage.
Gear clamps

You can never have enough. Photo booths in particular seem to generate a new mounting problem at every venue, and clamps are the universal answer to an unreasonable number of them.
Colored gaffer tape + multicolor Sharpies

Label cables, mark positions, organize cases, make temporary fixes, and identify gear. This is one of the cheapest ways to make a complicated event setup feel more controlled.
Replaceable photobooth props
Silly masks, outrageous sunglasses, and oversized objects do not need to be precious. If you run photo booths, people are hard on props. Buy fun things that photograph well and accept that some of them will have a short, glorious life.
Fun prop idea: A silly hat gives people something to play with while keeping their face in the photo. A hamburger hat is exactly the kind of ridiculous I mean. Everyone gets to look silly, and you can still tell who’s in the picture.