Do you cast on the first row of knitting?
The cast on itself is not counted, however, some cast on methods create both a cast on and a knitted row. For example, the most popular cast on, the long tail method, creates both a cast on and a knitted row. So in this case, you would count that as the first row.
What is the advantage of casting on thumb method?
The advantages of the thumb cast on: It creates a stretchy cast on and therefore is suitable for garments that need give e.g. sock and mitt cuffs (a revelation for me as hinted at in the introduction above!) It is simple to do in the middle of your knitting as you continue to work in the same direction.