Bibs are essentially lycra cycling shorts with built in suspenders. Its more coverage than a short and less than a onesie/full shirt.
Layers are totally where its at with cycling in the cold. If you are working out (pedaling hard and not just throttling) an old cycling rule of thumb is to be really cold on the first mile, then your body heat from exertion makes up for it. In other words you learn to underdress. If you don't, you sweat and thats worse. Get it right and you are perfectly comfortable in the cold and not sweating while pedaling and getting a workout.
Otherwise... if you are just cruising and throttling you wear another layer or two. So... what does "layers" mean?
In dry weather in your temperatures, it starts out with a long sleeve t-shirt. Thats your against-the-skin warm 'base' layer. The top layer - to stop the wind - can be nothing more than a thin windbreaker. Think soft shell rain jacket. Its thin but because it stops wind coming in, it also traps heat in. So you have very few layers on, and this may be fine for 50-degree weather. If not, layer on a short sleeve t-shirt over the long-sleeve base layer. Don't do another long sleeve layer because with your base and your outer layer your arms already have two layers. Step this up another notch a little differently: Base layer of a simple short sleeve cotton t-shirt. Second layer of a cotton zip-up hoodie (the zip up lets you unzip a little if you start heating up) and outer layer of soft shell rain jacket.
My outer layer soft shell was a Condor Summit Zero for many years, and I still have it. This is a jacket good at 50 degrees with a t shirt no problem and, really, its good down into the 30's with two layers underneath. It also gives excellent freedom of movement. Note I am specifying the Summit Zero and not the heavier Summit, which is a great jacket in and of itself but even though its thin its pretty heavy. Here's a link. The product page says "Men's Modern" but all the info down lower still says "Summit Zero". NOTE this jacket runs small in sizing. Probably you should go up two sizes from your usual.
I said the Condor "was" my go-to, and thats because I have replaced it with something that gives me dramatically more safety. Its a Proviz Reflect360 jacket. Its a big deal because basically the jacket looks like an ordinary grey jacket in daytime, but in twilight or night time, its all one
giant super-bright silver reflector, all over. The effect is astonishing and NO ONE coming at you in a car will ever miss your presence. I have had drivers roll down their windows at intersections and tell me how amazing it looks. And cars about to cross in front of me instead stop dead and just stare as I go safely by.
They run super-small. I normally wear an XL and needed a 3XL because of tight body and shoulders. That oversized, the sleeves are perfect for reaching forward all the time in a riding posture. But be advised they are rated as a rain coat, and breathe like a garbage bag. I combat this by wearing fewer layers, and unzipping the pit zips and half-zipping the front if thats not enough. Wearing a t shirt and the jacket alone is perfect in our 50's coastal weather.
Gloves: Polypro glove liners and deerskin gardening gloves over top. Warm and protective in case of a crash. Socks: Woolens from Costco if down in the 30's. Pants: Duluth Trading DuluthFlex cargo pants. Full leg coverage, and the 'flex' they advertise gives them a spandex-like give that makes them as comfy as cycling shorts in the waist and the legs. No constriction at all. Plenty warm on a cool 50's to 30's winter day. The ski mask
@biknut links is perfect for mild cold too. You can pull it down if need be and its thin enough to fit under a helmet.
It gets to the 50's and 30's here with a biting wind coming off the ocean, so thats what I dress for.