stole is knitted on the long side, so circular needles are easier to keep the 300 stitches.
Shawl can be done in straight rectangle without tassels and of course in only one color if wished.
In three colors and with tassels you’ll need : 40 gr for upper color, 30 gr middle and 40 gr of the last one (+5 gr of this one if you want add tassels)