I used a bulky weight wool blend yarn...I'm not good at remembering the kind, but it wasn't boutique yarn or anything. It was maybe $4.50/skein? I used one skein.
If you knit, here's what I did, if you don't feel free to skip the following paragraph:
I cast on 96 stitches, in the round, size 7 circular needles, did 2X2 rib until it was long enough (5"? 6?). Then I switched to double-pointed needles, knit one round as K2 P2Tog, then I did a K2P1 rib for a couple rows, then I knit a round of K2Tog P1, then a couple K1P1 rows, then I just kept k2tog until I only had 12 stitches left, and then I cut of the yarn and pulled it tight and threaded it back into the hat.Anyhow, it looks a little wide and poofy, but that is because Gabriel has an unusual amount of unusually lofty hair. On other little kids it looks how it is supposed to. I think Gabriel needs one of those poofy hats to hold his hair.
Gabriel wouldn't let me take it off to photograph it, but that means he likes it, so I'm marking that in the win column.