Usually trousers (really like the Eddie Bauer Ranier pants and shorts), golf shirt, grip6 belt, hiking boots and good socks. Bose QC35s if I’m in the data center. One customer makes me wear a safety vest. If I’m working weekends, in some data centers it’s warm enough for shorts (I’m not doing hardware installs).
If I’m working at home, whatever I slept in plus a shirt.