Scarves are the second-most-popular first project after hats — and unlike hats, they don't require working in the round, so they're easier still. A 6-foot rectangle worked in worsted weight uses about 350–500 yards.
Drape matters more than gauge for scarves: superwash wool, merino, and bamboo blends drape softly; stiff acrylics drape like cardboard. If the pattern recommends a particular weight, sticking to that weight will give you the intended feel.