Don’t forget that a full rain suit provides other options besides protection from rain. It provides great wind protection on cold, windy days, and even add a lot of extra warmth to your standard clothes to the point that often it’s feasible to avoid bringing along a warmer jacket. If it’s warm and rainy, wearing nothing but synthetic long johns under a rain suit works well.
Besides the usual synthetic clothing, don’t forget socks. I wear a synthetic liner sock under a light wool sock for most paddling, but the liner sock is mainly to keep the wool sock clean for a longer time.
Speaking of wool, wool pants and shirts are tough to beat (SO much more comfortable in damp weather than the jeans and T-shirts I wore before I figured out this stuff). They are terribly expensive to buy new, but sometimes they are still available through military-surplus stores at bargain prices. I always wear synthetic long johns under wool, mainly to keep the wool clean longer.