Depends on the conditions. I usually bike with him
If I’m walking and it’s wet, and it’s going to be muddy and or in long grass, then its usually wellies. Get good ones, not crap ones, I have muck boots and would recommend these
Hiking boots are OK, but they’re a lot more faff than wellies. Wellies don’t need to ‘dry out’, they slip on and off easy, then don’t need cleaning, they don’t need looking after
The only downside is they don’t really breathe, but I’ve never found it a problem
It’s worth spending good money on wellies, they’re really handy for dog walking
For trousers it doesn’t really matter. Jeans, walking trousers, combats etc. Once you’ve got wellies on they protect whatever you’re walking in