Why I put a laugh emoticon
This post makes me laugh with the simplicity of the post and considering he didn't even go check for past posts of this topic.
How do I "buy" from the storebot?
There is a command, !storebot, you can trade your credits away for real tf2 currency, metal. The reverse is also the same.
Why does it have nothing to trade?
They might have nothing to trade because people have already traded the items.
How do you restock the storebot?
Refilling the storebot is not an easy process, some people can buy a perk here called Donator. After the transaction is complete, Benedevil will transfer the metal and keys to the storebot's inventory.
How can I buy this perk?
Benedevil, the owner and the guy who manages the storebot.
Have a good day!