I’d say to add a sign or something to show how much everything costs. It saves the customer the from having to ask and you from having to say 
I’m honestly not too good when it comes to making the booth look nice since I’m also still learning, but I’m sure you can find some references.
If you’re not sure what to make, you could check this out. It’s a list of items that I made for my last market with links to the patterns (free and mostly no-sew/low-sew).