Just get good quality underwear. Tights or neopreme long underwear (under shorts unless you are very comfortable) and something lighter (like a jersey) for the top. I learned long ago that all the effort expended trying to stay dry is better spent trying to stay warm. Once the weather warms up getting wet is no big deal. Until then long underwear and wool.

Rain is about attitude not gear.

Also important: Don't forget a dry pair of wool socks for the ride home. The wool is great but the socks in particular seem to take forever to dry.