Photo from here.
Katy Perry is too unpredictable in terms of her fashion sense... hit or miss in fact. This sparkling black and white number, however, is definitely a hit from head to toe. You can copy the look for less.
Although not sparkly, this top by Forever21 is good to wear during the day or night. This is only $13.80.
If the lace-up side is too racy for you, try this Arden B miniskirt for $39.