Some clothing has to be ready for more than just the spotlight; it has to be ready for immortality. Drag queen clothing is not as simple as it would seem to be able to use, but the main criteria are that it must be gorgeous and it must be reminiscent of another era; fortunately, there are plenty of clothes that qualify.
For some, there is an additional advantage if the clothing has some sort of innate flash, such as sewn-in jewelry, but as long as it looks great, fits great, and allows for some motion the clothes work. While it is an additional bonus if the clothes can be worn on stage or allow the drag queen to dress as a starlet from a past era, these are merely bonuses; she is looking for something gorgeous and that is all that ultimately matters.