To me bicycle specific clothes was something of a revelation. It just plain works for me; it keeps me from overheating and get that clammy sweaty spot on the back, it keeps me from freezing too. If I get caught in a downpour I might get wet, but I don't get cold. (I really hated cycling in wet jeans before). It saves wear and tear on my normal clothes, and I always have fresh clothes and shoes when changing at work. The downsides are logistics; you need to carry clothes and change at your destination, and price of course. IMHO. the faster you ride, the better you will appreciate bicycle clothes.

To get some benefit at a low price, try layered dressing with some kind of wicking layer underneath it all. That works very well against getting sweaty and cold. I use a (non-bicycle specific) 100% pure merino wool wicking layer: they are anti-bacterial and only needs air-drying most of the time to stay fresh. A couple in rotation will last a long time before they need washing.
Thrift store Merino wool or Cashmere sweaters also works well as a middle layer. They don't stop wind as well as bicycle jerseys, so often they work best as a middle layer. Wool can absorb a lot of water (sweat/rain) before feeling "wet" and clammy, so they will keep you warm even if you get wet.

Some bicycle wind breakers can pack so small that they are easy to carry around, so if you suddenly run into high wind or rain, or falling temperatures, you can quickly "upgrade" your layers to cope with the changing weather.

Bicycle tights /bibs are very comfortable, but the padding requires a high degree of hygiene, so frequent washing is required, and more than one pair is highly desirable for commuters. In the winter or on cold rain, I use my regular short legged bibs toegether with a semi-water and wind repellent pair of long winter tights /without/ padding. That way I can use my cheap bibs in rotation, and get by with just one pair of long winter tights that rarely needs washing because it doesn't have padding.

There is a lot to save when buying on sales; I bought most of my winter bicycle clothes in summer sales, and my summer clothing in winter sales.

I bought one of my winter jackets at full price, but it has served me well for many years now.

A wool "Buff" is a versatile piece of winter equipment, and a regular cycling cap helps to keep the rain and snow out of my eyes.

To sum up; use layered clothing http://en.wikipedia.org/wiki/Layered_clothing
Start with a wicking layer.
Wool is nice choice for winter commuters.
Buy smart.
Bicycle clothes, and the amount of layers you want, is highly personal; what works for me, may not work for you.

I used to dread cycling in miserable weather, but in my bicycle clothes I just smile at the rain and snow.

--
Regards