I will say with this pattern I had to use two balls of yarn and follow the pattern directions for increasing, I went up to 40 stitches but actually could have gone even further making it longer.
This second scarf is the one to stash away for Christmas. I loved the wavy looking pattern of this. It is very easy to knit and also the pattern is on ravelry. I am really liking ravelry, such a large easily searchable database of patterns. This was wool yarn I had on hand. But I think it would be nice done with blue yarn as well. Sort of like the ocean.
I took this picture at night in my kitchen, which doesn't have the best lighting. But I think you get the idea of the pattern.