Square with Squiggles
By using a yarn with a long changing color way with one strand from the inside and one from the outside of the skein you get incredible color combinations. Increases and decreases in the ribbing actually create the pattern, so it is a bit slower than regular stranded knitting, but hardly any more complicated. Requires ability to read charts, knit in the round, do stranded knitting and 3 needle bind off for the finish. The corkscrew tassel construction is also explained.
One skein is plenty to make a hat even in the largest size, but then you will need to divide in half to work with one strand from the inside and one from the outside.