first get a chest and a sign.second place the chest then the sign above it then on the sign write your name
baxterdew then write the number you want them to buy or sell.fourth write B the amount you want them to buy it for
200 or S for sell if you want buy and sell do B 12:S 8 then below that write the item.Now you know how to make a shop:

baxterdew
3
B 250:S 100
Diamond