A shop, like Nook's Cranny, can contain just any items you want in your shop. Only put items in your shop if you want to sell them. A shop isn't an auction, so you would just post your items and wait for people to buy them. Here is the format:
Item One: Price:
Item Two: Price
Do not put Item One, and so on. Put the name of the item, then put price:, and then the number and then Bells.
Put the name of your shop on the name of the topic.
ONLY ONE PERSON CAN RUN A SHOP!!