Question Kit PvP Server

Okay so I was going to start a kit pvp server and I have come across a problem. It's not a big problem, but what it is, when a player has choosen a kit, I would like the Item/Shop to go away to prevent getting another kit. One other problem is I have KitAdder, but when I add custom potions, it spawns back a potion with no effects.
Here is a video:
Like I said it's just a tiny problem.