Dear Sir/Madam
There is a plugin call GuiShopManager [BS] it is a good plugin for making ingame shop and i kindly like u to add that plugin please
Plugman Link : https://www.spigotmc.org/resources/guishopmanager-bs.24757/
Description:
GuiShopManager allows to open Inventory GUIs (For example Shops) with clicking an Item
GuiShopManager works with BossShop, the most player-friendly GUIShop Plugin!