DHB thermal tights, jacket, socks, overshoes, gloves, neck tube, skull cap and Craft windstopper under layer, DHB is great value IMO and lasts plenty long enough if looked after.
One question I do have is what is the best way to keep your crown jewels from getting overly cold? I usually just chuck a sock in there but there must be a better way?
I have a craft windstopper layer as well - it is money on cold descents but when a jacket or vest would be too much.
On a mountain bike it is my Pearl Izumi Pro softshell jacket. On my road bike it is my 7mesh Corsa softshell jacket. The latter is super light, super thin and yet keeps me warm as long as I keep moving.
Pearl izumi Amfib bib tights and Northwave Raptor gore tex boots. Nice and toasty for those wet and cold winter rides!
A shed 
My favorite cold weather kit is my trainer. Seriously, has changed my parameters on when to go outside tremendously.
For anything 40F or above, The Black Knickers seem to do the trick for me. I also layer with a simple base, jersey, wind vest, sleeves, wool socks, and toe covers.
Anything below 40F, Gore Wear full length Thermal tights and Castelli Gabba 2, instead of the knickers and jersey/vest combo.
+1 on castelli, especially on the full winter jackets. I’ve found that outer layers for winter or rain its worth spending $ on and going with established brands (like castelli, ALE, Gore, Pearl, Cappo, Assos etc).
I used to work in the outdoor apparel and cycling apparel industries and can tell you that anybody can sew together a light to mid temp jersey but when you get into winter/waterproof jacket’s multiple insulation layers, waterproofing, zippers, welding and just overall fit it takes decades of trial and error to dial in warmth and functionality. These smaller brands are relying on a factory that will say they can do anything when in fact they are probably just leaning it.
Bigger brands have it dialed and its worth paying for outer layers.
oh and plus 1 on neoprene gloves…they are the bomb…but they smell like a stink bomb.
After really liking the chamois on Pactimo 12-hour bibs decided to try out the Alpine thermal bib tights. Pretty sure they were on sale for $110 or $120, and they have been great. Favorite feature is mesh pockets on legs and I use that to store and easily access food.
Also picked up Assos Mille GT Winter jacket and it has been awesome from 30F / -1C to 60F / 15C. Rode in the rain on Friday and its like one of my best ski jackets (we often ski in mixed snow and rain at Lake Tahoe ski resorts).
The aforementioned Gabba is my favourite bit of winter kit. I’ve got other kit that works as well weatherwise but they don’t fit as good as the Gabba.
I got the same alpine thermal bib tights on sale but have yet to try them. How cold have you worn them so far?
30F / -1C and they were fine. That day I had a cheap Costco long-sleeve base layer (32 Degrees brand) and the Assos Mille GT Winter jacket. I run fairly warm except for hands and feet, and could imagine someone else using a base layer and jersey underneath. I’ve done thermal arm warmers and summer jersey instead of the long-sleeve base layer.
Last week it was raining with temps 48F / 9C and I wore the Alpine thermals with a short-sleeve base layer and the Assos jacket. The short-sleeve base was perfect for temps.
It was cold for southern England (4 degrees C with wind chill) and the rain was bucketing down at the weekend, perfect conditions for Rapha’s second most niche article of clothing: the insulated pro team shakedry jacket. That plus their thermal base layer and cargo bib tights were perfect; didn’t get too hot on the only significant climb or the fast busy road sections, nor cold during the relaxed three hour cruise. Rest of my kit list was: Castelli neoprene overshoes over my only road shoes (Tri shoes, no less, the least insulated kind of cycling shoe on planet earth) and merino socks. Two layers of Dissent133 gloves (the mid and waterproof). Helmet and glasses too.
Reckon I might survive the Festive 500 after all 
I’m going to do some rides outside this winter and am wondering what clothing recommendations for temps 40F - 50F (4C - 10C). I have the Castelli Flanders long sleeve baselayer, but no long sleeve cycling jersey. I probably need some tights, too. I don’t want to spend a fortune but a few hundred for a nice pair of tights and a jersey is good. Also, I have gloves and shoe covers. Any recs to keep the head and ears warm?
Personally, I prefer leg warmers over tights…cheaper, more comfortable and versatile. I wear my normal shorts down to about 40* w/ leg warmers and have no issues. below that and I will use thermal bib shorts and leg warmers. below that, I am ridng inside. 
Go to Steep & Cheap for deal on all sorts of clothing options…
I have a myriad of clothing combinations and will adjust as necessary…but in general:
35-40*: Thermal jersey, LS baselayer, possibly windbreaker, leg warmers, thermal shorts.
40-45*: leg warmers, maybe thermal shorts, LS baselayer, thick LS jersey, vest.
45-50*: same but thinner baselayer or jersey.
For your head, a beanie under your helmet is nice but I’m fine down into the low 40’s in a regular retro cycling cap.
Some kind of neck thingy is really nice. Keeping the wind off your neck makes whatever else you are wearing feel warmer and you can pull it up over your face and ears if needed
Underarmour Coldgear is like witchcraft, i use mine for biking in cold weather, skiing, etc… it tends to keep me hot in cold temps even though it’s super thin.
Merino wool baselayers are also great to have and praised by most artic sport circiles.
Windproof/waterproof top shell (zippable) is great to kill some of the cold from getting to your bones
Lobster finger gloves help keep heat in better
Good ol shoe covers.
A buff/gaiter that you can put up or pull down depending might cut off a lot of wind from entering as well.
If it snows (although you mentioned positive temps) ski goggles might be something else you want to add
I also bought a cheap pair of overpants, brand is SOBIKE (lol) and the front is windproof and the back is breathable. The reviews show that people can ride down to -10 C with those on and not feel cold.
But it’s always kinda hard to gauge the cold, sometimes it seeps in, sometimes it doesn’t.
I’ll start off by saying I’m usually ok in colder temps than most people I ride with, in that I wear less at lower temps so adjust my temps below accordingly.
Starting from the top, I wear a PI thermal skullcap below 10ish (50) that covers the ears. Regular cap above that works too. Below 5C I wear a thin Buff neck warmer just to keep the chill off. Can pull it up over the chin if needed.
I have a couple older Castelli Prologo winter jerseys with windstopper that I wear below 16/61. For my birthday this year the wife got me a lovely Castelli Perfetto convertible which while a bit pricey is amazeballs. Below 10/50 I add a long sleeved base layer. Costco near me has merino wool ones (Paradox) for like 20 bucks and they work great.
Full finger gloves below about 10-12c.
I tend to agree with @Power13, I prefer leg warmers over tights for temps to the low single digits C (40F-ish) with normal shorts. Below that I have some thermal bib tights I wear.
Thin smartwool cycling socks and booties below 10/50ish.
Experiment with layering. One thing I learned though, if you are going for anything other than a really easy ride you should start off feeling a little cold. It will pass once you warm up. If you are comfortably warm while rolling out the driveway, you are probably over dressed, but that’s what layering and jersey pockets are for I guess. 
Haha…this just shows how individual cold weather gear can be…because when I read what you wear at different temps, my reaction was “good lord, I would melt wearing that at those temps!!”
I don’t break out the Windstopper material until it is below 4* / 40*…at 16*/61* I would wear a SS baselayer, regular jersey and arm warmers…knee warmers would be dependent on the day.
Haha, I just wear summer gear above 16/61, no arm/knee warmers really, except first thing starting out. My older LS jerseys are quite old and not super warm, there is just some windstopper on the chest. The new one I don’t need a base layer really until about 8C.
I guess the takeaway here is everyone is individual and experiment to see what works for you and for the ride you are doing. If I’m hitting some local climbs I’m shedding layers much more so than if I’m just doing a flat endurance ride. 
I regularly ride down to -3 C in winter, and i hate being cold
My clothing on those coldest mornings usually consists of
Skull cap under helmet
Buff (sometimes)
Wind jacket or rain jacket
Long sleeve merino jersey
Long sleeve merino base layer
Winter long bibs (brushed fleece inner)
Merino socks (sometimes a 2nd pair of socks)
Neoprene overshoes or toe covers, doesnt really seem to be much difference between full overshoes vs toe warmers in my experience
When/If it warms up, i can ditch the wind jacket, and still be comfortable
The other options i have are a softshell long sleeve jersey, which I still wear with a long sleeve base layer, but I find its not as warm, probably a fine option for your temp range though