You can get a thin smartwool or polypro base layer from a ski shop for like $50, even cheaper on sale but it’s the wrong time of year for that. That’s probably all you would need unless you’re planning on running in a blizzard.

When I was in the military a bazillion years ago, our winter running uniform was a beanie to add to our t-shirt and shorts. That was it. If it was SUPER cold (like, below freezing) we’d get to wear sweatpants and a sweatshirt. Then we’d go run 4 miles in the dark. If you got too cold you just had to run faster. :)

I run outdoors year-round in weather down to 20°F in a climate with high humidity. Above 40°F I wear old beat-up tshirts, a thick hoodie, and leggings-style running pants. Below 40°F I replace the T-shirt with an REI house-brand light- or mid-weight base layer, and I toss a pair of cotton exercise pants over the running pants (I bought those years ago for less than $15) and wear a cheap woven hat and my junkiest gloves. If it’s raining I’ll replace the heavy hoodie with a water-repellant windbreaker + light weight hoodie.

In other words my running wardrobe is comprised almost entirely of my oldest, most beat-up clothes, most of which were originally just cotton or other cheap non-technical materials purchased years ago at a fast-fashion store at the mall or used from a sporting goods store. I do invest in decent socks (I highly recommend darn tough for their durability), but unless you’re braving truly cold temps, very long workouts, or cannot return indoors shortly after working out,* you really don’t need anything fancy for year-round exercise. For what it’s worth I’m also a woman and I get cold very easily.

*The main problem with cotton is that it will not keep you warm when wet, so if you like to take a long cool down walk or hang out on a park bench for thirty minutes post-workout you should go with wool or synthetic material so you don’t freeze in your sweat-soaked clothes. But as long as you’re returning to a warm indoor space before your exercise warmth dissipates, this shouldn’t be an issue.

What type of weather are you running in? In my area it gets just below freezing in the winter, and I run with a full length compression shirt, then a technical running tee, then a fleece jacket. Works in wind, rain and snow between around 12c and -4c. Leggings and head/face covering are also often needed.

Biggest thing for me is really socks and runners; socks are wicking insulated running socks with an ankle, shoes have GoreTex uppers to keep my feet warm and dry.

Something to also take into consideration is how hard you’re pushing/sweating.

Merino wool will definitely work as a mid layer, but you’ll likely overheat pretty quickly, and it’s hard to get the sweat out.

As the hikers say. Cotton kills…it retains water (sweat / rain / snow) and ends up being less insulating, making you susceptible to hypothermia and making the layer heavier. Typically the base layer is there to wick water away from your skin, and the mid layer is there to keep you warm. Any temp under 40f, is considered a no go, with cotton, if your hiking.

Looking at clothing recommendations, here, and here for runners, it seems if it’s under 30f, they tend to stay away from cotton. Note: Obviously these people are also selling expensive clothing, whats important is the fabric type, not the brand name. Even if your not at risk of hypothermia, the cold constricts your muscles, making them tighter, which apparently is not great for running.

To answer your question, as long as it’s not Kari Tra brand wools, (esp the thin ones, get holes, practically immediately, for no reason. The mid weights are better, but not by much) imo, as a hiker not a runner, i would say they should hold up for at least a season, with proper care. Especially, if your wearing something more slippery like polyester over them. Wool definitely breaks apart due to friction. Even wools Ive gotten to wear under work clothes, only last a couple years max, before they start to wear in some choice areas. If you value your wools though, I would find some polyester / synthetic base / mid layers, especially if you are running on a regular basis.

Tldr: if your running in freezing temps don’t wear cotton. If you value your wools, get a polyester / synthetic base and mid layer. Also, maybe check out REI brand for some cheaper wool layers.

I’m from Minnesota and I used to run to and from work and go trail running on pretty desolate mixed use trails, so my advice might not applicable if you aren’t running in that kind of environment, but here goes:

I’d go way overboard on the digits and the ears, toasty when standing around, and layer my core fairly light: underarmor-type long sleeve compression, long sleeve shirt, then fleece or a windbreaker (full zipper). Basically kinda chilly but not shivering when standing around. If it’s like -20F I bust out the wool, balaclava (sp?), and ski goggles. Goal is to be able to unzip and open things up and not get too hot and sweaty, not rely on physical activity to keep fingers and toes warm. When it’s too cold and you aren’t crossing paths with many people, an easily-overlooked danger is injury or incapacitation. You wanna be dressed to the point that you could just lie on the ground for a couple hours, take a nap, and not wind up with frostbite (or worse), because ice is fun and shit happens. If you’re gonna be running in that kind of cold, it’s a good thing to keep in mind, kinda like how people say to throw a blanket in the trunk just in case your car breaks down, you’ll probably never use it but it’s good to plan around a bad scenario