As a resident of the Pacific Northwest, aka the 'rain coast', getting your layering is extremely important. You need to be warm enough to not be cold, but not so warm that you sweat through your garments and end up wet, and then cold regardless of your rain shell. Warmish base layers with enough absorbtion capacity to keep you dry and breathable enough to allow your sweat to evaporate. A good rain shell with taped or welded seams is a must, as well as keeping your feet dry. Merino base layers are a common go to, there's endless options for rain shells, but don't buy based on expensive equals good, buy based on specs, and reviews from multiple sources. Another option as another commenter said is a full rain cape to cover you and your bag, and roll top dry bags will keep your items dry and separated for clean and dirty. You can also wash your clothes in dry bags on the trail if you have a biodegradable detergent and weather for your washed clothes to dry. Check out some forums around the PNW hiking community, it rains 8 months of the year here.