Wear black heels. They are more supportive and professional. And I seriously doubt that you Have to wear leggings. They are not ever appropriate for work. Wear long black flared dress pants.
You can get insoles from Dr, Scholl's for your shoes and they even have them for heels. Try those first before splurging on another pair of shoes.
Duty shoes, or running/walking shoes. Check the dress code where you work.
I used to work 12 hours sifts each day standing+walking all day. At first it sucks. Later on, your feet muscles will adjust. This is a type of a problem that fixes itself. In the end I got a chair and I never couldn't remember to actually use it because I had no problem standing all days long any longer.