Silicon Valley rating system on a sliding scale from more formal to least in each category:
Formal - Tux
Business Professional - Suit & Tie, Slacks & sport coat, Slacks & button down
Business Casual - Slacks & Button Down, Chinos & Polo.
Casual - Jeans & button down, Jeans & Polo/Jeans & Sweater, Jeans & hoodie, software engineer not giving a fuck
Shine your damn shoes & wear a matching belt.
Work wear for me is years-old jeans, most with holes, 10-20 year-old T-shirts in various states...and/or usually the same fleece sport pullover the entire week.
Work for you guys sounds like prison.
BDUs. combat boots, and a Tshirt. For dressy occasions, replace the Tshirt with a button up. Go Hawaiian for an eclectic touch.
Nice shirt, no tie, nice slacks, comfy loafers.