Changing your Pokémon Trainer's clothing can add more personality to your Pokémon journey, and you can do so in Pokémon Brilliant Diamond and Brilliant Pearl. Unfortunately, you may have to wait a while before you can unlock this option. Here's what you need to know about changing your costume in Pokémon Brilliant Diamond and Brilliant Pearl.
You can do this at the Metronome Style Shop. On the map it will simply be called Style Shop. You can find this shop in Veilstone City, which is a location you will reach when you are ready to fight the third Gym Leader, Maylene. You will be able to reach this city by going east of Celestic City, from Route 210, on Route 215.
When you are there, we recommend that you go to the southwestern part of the map and find the metronome style shop. Enter and you will find a woman directly behind a counter. He talks to her and tell her you'd like to shop around for a new dress. Next, you will enter a new menu where you can choose from a variety of outfits for your trainer. You can also preview each outfit before purchasing it. The dresses cost quite a bit of money, random from 90.000 to 120.000, but there are cheaper dresses you can choose to buy.
After purchasing the item, talk to the woman again and ask to change your style. You will then be able to choose any item you have purchased and wear it on your character.