For our displays we use black foam board from hobby lobby and staple them to some home made wooden easels made out of some scrap wood we had laying around. They're kind of heavy, but they have to be for when we do outdoor shows.
I painted the easels black, and the foam board is black, and I put white decals on them to display. After 1 year of use, they look a little faded, but I planned on changing up my displays anyways (replacing what didn't sell with something that might). Your best bet might be to make a little bit of everything, find out what people are interested in buying, then go from there.
The easels are ideal for us because we can switch up the foam boards and display different items for different shows, different crowds. Also, it doesn't matter if we're on pavement. I've seen at the one fair people set up and nail coroplast signs into the ground, which looks great but it obviously wouldn't work on pavement. I like having 1 set up, regardless of what we're on.
You mentioned lots of golf carts - I'm sure it goes without saying, have lots of golf themed work done up! License plates, plate frames, car decals. Anything a golf enthusiast would want to buy.
Good luck!!