More bagcheck answer...
I tend to totally change afterwards. I just don't want to be in those clothes anymore; they are too sweaty, and even after the '13 TOT when it was so hot I got chilled VERY quickly after the finish. I want to get into a bathroom, take care of bathroom stuff, and change from head to toe. So I tend to pack underclothes, a yoga dress, a warm top, and fresh compression sleeves. And flipflops.
Crocs to be specific; I had DH bring me my new Sanuk flips with a complicated cloth thing on top and it exhausted me to get into them, LOL. Simple is good.
A new hair tie is good, too, or my little clips to put my soaking hair up in a bun. Oh and a small towel to try to dry off the hair.
If the Garmin stresses you and you don't like the info it gives you during and/or after, no reason to have it.
Does your skirt pocket have a zip so the band cannot fall out? That would be bad to lose it.
No one is going to try to find you after the run? If you're solo and no one wants a phone call, no need to have a phone. I do carry one with me because DH is as big a worrywart as I am, and I ran my first Disney race without one and for me/us it was a big mistake.
I've been slowly decreasing the things I need both because carrying a hydration backpack is annoying and sloshy and also because as my base fitness level improves I don't need all of it. I do carry sports beans and/or shot bloks, and a small bottle with a serving or two of Clif brand electrolyte drink. I now drink the water on the course (my stomach is sensitive so I was avoiding it, but avoiding it wasn't creating any different situations), and as I drink the water I drink my not-diluted-enough Clif drink. The MB didn't seem to bug me and running with the other wristbands didn't bug me either.
I also tend to bring a CC and some cash in a snack sized zip top, either in my shorts pocket or small running belt.
And believe it or not that's LESS than I used to bring.