For this achievement, you will have to dress like the picture on the wall next to the Cashier.
If you are a male, it's on the right. If you're a female the picture is to the left.
All clothes required for this achievement is purchasable only in the Casino shop to the right of the entrance to the casino. The hairstyles/colours you will have to attend a Barber to change.
Hairstyle - Short Cut 4
Hair Colour - Auburn
Facial Hair - Clean
Now match the clothes and sunglasses with the picture in the lobby.
Hairstyle - Short Half Length Cut 1
Hair Colour - Red
Again, match the clothes with the picture.
I'd like to say again, all clothes required are ONLY available from the Casino store.