This scarf was designed as a scalene triangle so, while there are decreases on one edge, there are increases on the other edge. The design features a large cable and texture poinsettia flower on a stockinette background with seed stitch borders. The cast on edge is the shortest side, about 27" (68 cm) so plan your needle length accordingly.
The sample was knit with Softball Cotton Featherweight which is a loosely spun, fingering weight yarn. A sport weight yarn could also be used on the same size needles to get a little denser, crisper fabric.
The sample took 599 yards, so I'm saying 600 yards (548 m) is the minimum amount of yarn you need.
I would suggest 11 stitch markers - one at each border and the other 9 to help mark out the cable. You'll also want a tapestry needle for sewing in ends.