Winter is coming

[BleeckerSt_Girl]

Look for merino wool sweaters in thrift shops and Salvation Army. Merino is usually quite thin and soft but very warm.
Real wool is a good bet because if you take good care of it it will last you for years. In cold weather you don't sweat much and real wool does not get bacteria-caused body odor easily (like man-made fabrics do)- so you can probably wear wool items several times before needing to wash them.
You don't say where you live or hold cold it gets....but with your Underarmour leggings and then a thick pair of polarfleece pants/wool leggings/or windproof tights over them, you can bike into some pretty cold weather.

Get a warm helmet liner to keep your head and ears warm (look here on TE shopping area)- that helps a lot.
The hardest parts for me in temps in the 20'sF to keep warm are hands and feet. Again, 100% wool glove liners and good wool socks will serve you well. Since wool doesn't get smelly easily- you can often wear your wool socks several times before washing them.
You want to try to break up the cold wind on the outside....wear a warm thin top or two, covered by a good windbreaker. The windbreaker will keep your warm body heat in.
You don't really need a giant wardrobe- if you get a few good quality items, you can wear them over and over in the cold. Wearing 2 or 3 thin layers works better than one bulky layer.

[Torrilin]

I got a truly amazing haul at a thrift shop yesterday. 3 lightweight wool sweaters, for about $15. A pair of wool pants for $10. 2 of the sweaters go to my partner, who is a wee short on snuggly wool. The pants are for me. I should be able to bag another sweater or two for him for under $15. Add in some wool pants for each of us, and we'll have much of our layering taken care of.

Long underwear is also on the list. I'm watching the local Land's End Not Quite Perfect store for cheap silk long underwear. Keep your eyes open, you may have something similar nearby.

I have a respectable supply of handknit wool socks (yay for hobbies), and am working on his sock supply. Turning entertainment budget dollars into clothes doesn't work for everyone tho *g*. There are often good sales on wool socks in January. Same for other woolies.

I haven't figured out outer layers fully yet. I suspect it will vary based on conditions.