For cold, wet riding, make sure your bike is fitted with fenders.
There are lots of breathable waterproofs around. Some are better than others by a small degree. I think it is better to wear a waterproof when it rains, and a cheaper, more breathable windproof when it is dry.
Look for generous sizing, high neck, bright colours and reflective piping. I find a high chest pocket much more useful than a rear one.
I use a cheaper helmet with less ventelation, so I dont need a hat. I use a long neck-tube which I can use to cover my ears.
Use a generic wicking, long-sleeved jersey, you dont need to get premium branded stuff.
Use any available mid-layers. Woolly jumpers are pretty good.
To prep your bike, wash and wax the frame. Wax any exposed bolts. Grease the cables and any metal-metal contacts (like the seatpost and any bolt threads). Keep the chain lubes. That is all you need to do.