I'm a fairly new quilter myself and when I started stash building, I'd get fat quarters or a yard. I quickly found out that that is not enough unless you plan on making scrappy quilts. So now, I buy at least 2 yards. If I'm buying a lot of coordinating fabrics and intend to use them together, I might get 1 yard, but most often I buy 2. I usually buy fabric with intentions to use it together or for a specific project, but I rarely have an actual pattern in mind, therefore I rarely know how much I need of each fabric, and I've found a couple of times that I would much rather have too much than not enough. So far in my experience, having two yards of each fabric in my "plan" gives me plenty. Also, I don't often buy big print fabrics unless I'm buying for a specific project. I stick to blenders and neutrals for the most part and buy prints on an "as needed" basis.
I usually use bed sheets (most often flannel) for backing, so I don't often buy yardage to back my quilts.