The Style Shop is the place you can go to buy new clothes for your Pockie or change their style.
Where is Dress Up?
Tap the Dress Up icon in the main menu.
Where is the Closet?
Tap the Dress Up icon in the main menu, and then tap "Closet".
The Shop tab displays items that your Pockie doesn't currently own and for anything you do own, a wardrobe icon 
is displayed and you cannot buy the item again.
Anything you tap here will automatically be modeled on your Pockie, but not purchased unless you tap "Buy." If you cross out that item or go to a different menu item, your Pockie will revert to their previous look. However, if you switch categories, the unpurchased item your Pockie is modeling will stay on. If you try to leave the Shop without purchasing anything your Pockie is wearing, you will be prompted to buy everything at once. This can be an easy way to change your Pockie's look.
The Closet shows you items your Pockie already owns.
If you attempt to leave this area and you made some changes, the game will automatically ask if you'd like to save these changes.
Changing the gender of your Pockie doesn't make a difference in terms of the items that are available for you to buy.
Note: Many items that are available to you at the beginning of the game are available to purchase after you start the game.