The Item Shops are, as their name imply, places where Shantae can buy new items, generally in exchange for gems, to help her in her journey. There are five Item shops in Shantae, but only one in Shantae: Risky's Revenge and Shantae and the Pirate's Curse. Shantae: Half-Genie Hero has both a standard item shop and a second merchant in the form of Tuki. Shantae and the Seven Sirens features three Item Shops, one for each town.
In the first game, there are Item shops in the four main towns (namely Scuttle Town, Water Town, Oasis Town and Bandit Town) and one in the Zombie Caravan. The items are bought for gems, and vary slightly from one shop to another, notably the Zombie Caravan shop offers items at a lesser price than everywhere else, and the Water Town shop is the only one where Shantae can buy the power-up items, namely the Boots, the Sash, the Cuffs and the Tiara, which allow her to make additional attack moves.
In Risky's Revenge, as Shantae barely leaves the vicinity of Scuttle Town, the shop there is the only accessible one. Contrary to the first game, besides potions to refill health and the magic bar, the shop offers most of the power-ups and the magic spells that can be acquired in-game. As a further difference, gems are not the only accepted currency, as some items need to be bought for gems plus a varying number of Magic Jams, which are claimed by several characters including their creator, the Magic Jam Lady, to be extremely valued.
In Pirate's Curse, Scuttle Town's is the only shop again. It now sells upgrades for some Pirate Gear and a new move for Shantae, as well as hair upgrades and consumables.
In Shantae: Half-Genie Hero, Scuttle Town Square houses the main shop. In order to kick-start the plot, Shantae needs to retrieve an item from the Shopkeeper for her uncle, but after that, the shop can be perused as normal. It sells potions, secondary spells, and hair and defense upgrades for Shantae, as well as the Warp Dance.
There are also jars that can be found in certain places that contain Tuki. She sells potions and transformations that Shantae can learn.
In Shantae and the Seven Sirens, there is one shop per town (Arena Town, Tree Town, and Armor Town.) They primarily sell potions, hair upgrades, and secondary spells for Shantae, with minor differences in stock depending on which town she's shopping in. Some of them even expand their stock if Shantae has bought a lot of items from them.