You can sell things to the server, all worlds and everyone can see it. open the mainmenu item by right clicking with it, then clicking "shop menu" and then "player shops" at the top. it will list all player shops and tell you how to create your own at the bottom. The gifs on this wiki entry will also show a step by step of how to make your own shop and add items to it. You can also get to the player shops by doing /playershops or /market as a command. If you like making a physical shop in the world, you still can! place a sign on a chest with "[PlayerShop]" on the first line! if you place "[PlayerShops]" on the first line (with an s) you will be directed to the list of all player shops.