I have done a Peppar's Ghost effect on a shoestring. It depends on how creative you can get in obtaining a large enough piece of glass for the scene you are designing. I used an old sliding glass door that a friend replaced. I dressed around the frame to hide it, set it at the right angle, and had our actor appropriately placed so you only saw his reflection..instant ghost. placement and lighting are key.
If you can find a fabric to use as scrim material, then you open up a lot of fun things to do if you have access to projection equipment.
You can also create a "living decapitated head" effect using a 3 - legged table and two mirrors that fit between the legs, and have the table sit in an "alcove" in which the back and sides are identical. The mirrors reflect the sides, so when you look straight on, it looks like you are seeing the back wall under the table. Actor goes under table with head through a hole. Cool, cool effect.
Once your creative juices start flowing, you can come up with all sorts of different spins on the same techniques. A quick web search can bring up tons of sites with inspiration and how-tos.
Again, take time to tell your story through scene design, keeping in mind that your audience is on the move and only has a few seconds to "get the story". And remember to spend the time on lighting. Lighting is key.
(Can you guess that Halloween is my favorite holiday?)