I have an aisle Jacobsen raincoat that comes down below my knees and is properly waterproof and windproof. Helly Hansen also do longer than usual raincoats that are also windproof.
I would definitely think firstly about function - layers of merino wool underwear and good thick socks.
I have a pair of Meindl walking shoes that are incredibly comfortable and good for outdoors, although they were expensive.
But where we are, the sidelines up to 14 months ago were a mix of jeans, chords, tracksuits/leggings, slacks…and a broad mix of comfortable and warm tops on top. So nice leggings and a warm hoodie next to wool slacks and a chunky jumper next to chords and a couple of tops layered up under a wool cardigan.
lots of scarves, hats and thick gloves in winter. Everyone had a good coat - waterproof and windproof. A mix of sailing type jackets and waterproof trousers, the HH I mentioned above (similar to what you see on rugby sidelines), ski gear in depths of winter, or my kind that is more stylish for work rather than so functional looking (but incredibly functional in reality) - some waterproofs were less warm/padded and people layered up more under then.
There was almost never chat about clothes - more about the kids and the games and life in general and the weather…the weather!!!