We can't deny that looks sell.
For auditions, try to look your best. Unless your character is supposed to be grungy and homeless, you should be dressed business-casual.
Taking care of yourself doesn't mean only dress nicely. Try to make sure your hair and face are presentable.
If you need to shave, comb, trim, or do any sort of makeup- you should do that as well. Think of how you would want to look meeting a business partner for the first time.
Another way you can take care of yourself is through exercise. If you play the athlete, boxer, kayaker, dancer, or anything like that- you should look fit enough to be able to complete those activities.
You do not have to go to the gym frequently, you can work out at home or outside if the weather permits.
Be sure to take care of yourself!