My go-to quilt when I need to make one in a hurry is "I Just Can't Cut It."
For a large twin it requires 4 1/2" yards - so if it's a fabric appropriate to the pattern (shows 12" squares) I buy 5 or 6 yards.
Otherwise, if nothing in mind I buy, I'm likely to buy 3 or 4 yards.
I almost never buy FQs
On-line, I very rarely buy fabric that's not on sale.
Check our
http://www.hancocks-paducah.com always has fabric on sale starting at $3.98/yard.