so first start with how you get the item which of course is the shop! (wiring a button to it is optional but you can!) set the settings of the vending machine to whatever you want then connect it a wire repeater then wire the repeater to a checker with settings like this
then wire the checker to a game overlay (check passes show overlay) and the game overlay should not be visible on game start make sure the game overlay is a button and transmits on channel ¨has blue seed?¨ then wire the game overlay to a wire repeater (all should have 0.5 delay) and copy the check from b4 and delete the channel on it keep all the rest of the settings and wire the game overlay to the checker and grab an item granter set it to takes away selected item with the negative sign (example like -1) and a health granter wire the checker to both of those (check passes grant health|checkpasses grant item) and it should look like this
and wire the checker back to the game overlay (check fails hide overlay) you are done the finished product should look like this
if you are wondering what i have the shop wired to its a notification with (item failed to purchase send notification) and 3 buttons (button pressed attempt to purchase) and tell me if i need to credit any guides im not too sure if there are any… anyways have a good day meow! :3