It depends on how complicated the desing of the dress.
And what materials you want to use.
For $200, you can get materials from spotlight and tailor it at
some hdb neighboughood shops.
For Tanjong Pagar are, go to the Tanjong Pagar Hawker
Centre. There is lots of seamstress shops that tailors Chanel
replica jackets, pants and dresses.
For City Plaza at Paya Lebar, go to the ground floor shops.
For Katong Shopping Centre. Their basement has lots of
seamstress shops that can even do up cheong sums for your
price.