oilskin gets heavy in rain( i know...i wear them at work all the time) get one with some sort of sleeve at least, i prefer 3/4 sleeves myself.
Get a balaclava.....you can get thin ones at hunting and fishing or thicker oxford bike ones.
get a few multi layers of merino .....op shops or trade me are quite cheap compared to dogmandhu..
Bib pants (leather from trade me for me) keep you a lot warmer and drier then regular pants.
Enjoy the trip and stay warm...