Good winter biking gear?

Overshoes are a good idea.  Failing that, layers.  A set of cycling tights, with your mtb baggies over the top is good.  Base layer with a cycling shirt and a viable jacket.  Then look at a neck warmer, decent winter gloves, skull cap or cycling hat under your lid.Warm socks.

Remember, you should be cold when you start out and then warm up as you do work. Baggies over your shoes can help - your feet can get quite cold.

Make sure to use gloves. Cover your neck with a scarf. Cover your head with knitted cap. 

It’d help to know what ”winter” means for you.

Even with that, cold tolerance is VERY individual.

Me, I sweat very easily. What works for me is clothes with dissimilar panels. Wind proof fronts and ventilated backs. A wicking layer underneath. Reinforced with thin fleece as needed. 

Softshell would be too sealed for me.

Things I find important:

- bicycle specific pants/tights. There’s no guarantee a randomly chosen garment will withstand the friction from the saddle. No point in chewing up an otherwise perfectly fine pair of pants in an attempt avoid buying cycling pants. Some generic outdoor pants will tolerate cycling, but not all.

- pogies/bar mitts are great for hand warmth. With those, almost any gloves will do.

- I’m not a fan of shoe covers. They kinda-sorta work to keep your feet warmer, but it only takes a minimum of walking to turn them to shreds. Flatties and hiking boots or real winter cycling boots work better IMO.

Avoid pure cotton.  Yes, you can sweat, even in the winter.  Cotton traps moisture & locks it in.  Next thing ya know...you've got a bad cold or the flu.  I've bought most of my cold weather gear through Aero Tech Designs.  https://www.aerotechdesigns.com/cycling-tights.htm...

https://www.aerotechdesigns.com/merino-wool-cyclin...

https://www.aerotechdesigns.com/usa-softshell-cycl...

Get yourself a good balaclava & lobster gloves.  https://www.trekbikes.com/us/en_US/bike-clothing/c...

If you ski cross country or run during the winter that's a good place to start.  Wear what you would for that to begin with, and adjust for flexibility and wind resistance.

If you don't, then start with thin flexible full thermals, and layer as needed for additional warmth.  Your top layer - both torso and legs - should block the wind.  Just make sure the butt isn't slippery on the saddle.

Also remember your head and hands.  It's shocking how cold they can get during a ride if you forget the wind.  Wear long-fingered cycling gloves at a minimum.  If your helmet has enough adjustability, wear a snug ski hat or cycling skullcap under it.  If not, get a helmet cover from your bike shop.

They also make shoe covers for winter cycling.  I've never needed them, but my older brother does.