The outer layer is going to have all the muck thrown at it, and it will get mucky, so sartorial elegance isn’t the primary function here. As well, this layer is the first layer to get abraded, ripped or torn if you take a tumble. So you need to think this through.
For the last ten years (I kid you not) my outer layer of choice in wet/cold conditions has been the same Alpinestars RJ-5 rain jacket (and pants, when it gets super-wet). It’s a budget product (about £50 for the set back when I got mine – these days the jacket costs circa US$65/£35) but has proven highly practical, and sturdy.
It’s made of heavyweight rip-stop nylon, with a mesh liner, although it’s actually very light and is of a smock design (so no zip) and also oversize cut. Alpinestars call it water resistant yet mine has stayed waterproof through countless downpours over the years. I like the loose cut as it allows for body armour and several layers. The fact it flaps in the wind allows just enough airflow, too, so that you never get sweaty. Being so cheap it’s not going to be such a tragedy if you rip it up in a fall. Its got rudimentary Velcro adjustment everywhere except the hem and there’s a pouch pocket on the front (not waterproof, so sea-up any stuff you might store there).