Call me a cheap bastard, but I have a medium and a thicker base layer shirt and a couple of sets of britches from Walmart and Target that have served me quite well. I forget what the brand is, but it's basically the house brand. Champion or something like that, I think. Basically imitation UnderArmour.
These were, um, roadside purchases on unexpectedly chilly trips (Me? Plan? Never!), but they work better than I ever would have thought, and were quite inexpensive.
2002 Suzuki DL1000 V-Strom, Dark Metallic Space Blue
1983 Suzuki GS850G, Cosmic Blue
2005 KLR685, Aztec Red - Turd II.2, the ReReTurdening