Rode up to Connersville (3 hrs away) on Thursday for work @ approx 50 degrees / 80 pct humidity. Not bad, considering we were averaging 75+ all the way up there. Had on regular uniform pants (thinner than jeans, honestly), a hoodie and leather jacket over my uniform top and my Z1R unlined gloves. Was fine the whole trip.
Like I said, you don't have to get too frisky until the temps get into the low 40's or high 30's. Then, you consider 2 layers on the legs, fleece liners + leather gloves, balaclava or gaiter, 2 sets o' socks, base layer + hoodie + leather jacket w/liner (for "full" comfort - not necessary if riding less than an hour or staying off of highways).
Anyway, a lot of crap to pack. Saddlebags become a must to haul all this junk around in if you want to ride when it's cold. Fall is 30's in the morn, maybe low 70's during the day. Makes for weird riding clothes.
We don't have any extra ninja suits lying around but here's a flea-bay auction for them (Army Silkweight Undershirt/Pants):
2 Polartec Thermals Top Bottom L1 Gen III Silk Weight Military Army Medium Reg | eBay
I used to wear this stuff in Afghanistan under my regular uniform on foot patrols. We would move 10-15 miles in 15 degrees with a stout breeze and I'd be sweating like a champ when I got back. I assume it would be a good base layer for rides too. Military surplus is cheap enough and usually built to last. It fits a little tight, btw. If you don't like stuff tight on you, you may want to go with a larger size. I'm 6' 200lbs and I wear a large regular, for reference. If you can get the long version, go for it. That way you can tuck it into your gloves. The sleeves have thumb holes, which help.
They make another, heavier version that is polyproplyene but that crap itches like wool and you'll get cold because you'll sweat too much.