I ride year round in civil clothes. OK, pants I buy for hiking mountains are more comfy than regular jeans, but nothing bike specific. Bike specific is nice, but regular clothes should be enough. As you go, you will gain experience, see what works, what doesn't.

I sweat a lot. So I carry a big bag on bike's rack, to put extra clothes in as I get warmer. Often end up in just a sleaveless vest and t-shirt.

Good pair of glasses, skiing goggles when it's freezing cold, a band for protecting ears and forehead from cold wind, decent gloves. Pants that aren't too uncomfortable when wet. Some wind-stopper jacket, thin enough to pack easily. That should get you started.