I have 3 polo shirts, 3 sweatshirts, 1 waterproof fleece and a baseball cap, all with embroidered logo on that matches my van logo.
A pair of strong, durable trousers and decent boots during the winter.
In the summer it is shorts and the polo shirts.
I don't think it matters a whit what kind of shoes you wear, trainers, boots or whatever, just so long as they look reasonable.
Wearing clothes that are what could loosely be described as a 'uniform' is I think a good thing, it doesn't make you a better window cleaner of course, but it does give an impression of being professional.
It just looks way better than scruffy jeans and an old tee shirt (many don't wear new clothes to work, they've usually worn them socially first, ditto trainers, the ones worn to work are often those they wore out socially and have replaced with a new pair.)
But then, I wore such clothes to work for 22 years before I decided to 'logo up'.
It is also fairly cheap too. For 3 polo's, 3 sweats, a waterproof fleece and a baseball cap it cost me around £90, so it makes financial sense too.
Ian