Items in your inventory you can upgrade through the production process. Each item has its requirements for an upgrade which are written below the item's name, so pay attention before upgrading! The best way to get items is via auctions or visiting other players' supermarkets and taking them with force! Remember that each store has no more than five items at any given time, so choose wisely if there's more than one of the same item! You can also purchase items on the market, but be sure to check their price before purchasing!