I usually go to ground in the winter using a bivey, Big Agnes insulated pad and a down sleeping bag.
However, I have a some car-camping or short backpacking camp outs on the calendar for this fall, where temps will generally drop into the 40's.
I'm not ready to buy a quilt - when I do it will be a high quality down that I can use for extended backpacking trips.
So I was looking for ways to rig up an old sleeping bag as a quilt, then I found these quilts in Walmart for $16 (twin) and $22 (full/queen): Mainstays Reversible Microfiber Bedding Comforter
Either could easily be cut into desired dimensions, then have the open cuts sewn up. My plan, however, is to simply fold them in half, then use gator clips in place of loops to test them out as quilts.
Folded in half, the twin makes a 66 x 43 inch quilt. The full/queen is a bit too big folded in half - either 86 x 46 (which might work) or 92 x 43 (which would be better to cut down the length to 72).
I can get loops sewn on for less than $10 total if I decide to go that route so I can ditch the gator clips. If I cut the quilt, my seamstress will sew on the loops and sew up the ends for $15.
I can stuff the twin sized quilt into a medium sea-to-summit stuff sack. It weighs 44 oz (2 lbs, 12 oz). Using the full/queen would be limited strictly to car camping - more because of the bulk rather than the weight.
My next thought was to buy two of the twin sized quilts, have them each cut into 44 x 72 (or perhaps less), then have grosgrain loops sewn in each corner, then add snaps along the edges so that I could snap them together for colder temps, but just use one single layer for warmer temps. That would drop the weight of each layer to 24 oz (1lb 8oz) (sans the weight of the loops and snaps).
For about $60 (includes quilts and sewing) I think I'd end up with a usable under quilt system, albeit not ideal and not as good as what I'm looking to eventually purchase.