These are a few of the crochet edgings I use on my donated caps, collected here for simplicity.
3×3 picot (worked over a multiple of 3 sts):
Ch 1, sc in next st, ch 3, sl st in the same st as the last sc, [3 sc, ch 3, sl st in. the same st as the last sc] until 1 st left, sc. If working in the round, join to ch 1 and end off.
3×3 loop (worked over a multiple of 3 sts):
Same as 3×3 picot, but skip the sl st after each ch 3
2×3 loop (worked over an even number of sts):
Same as 3×3 loop, but do 2sc per repeat instead if 3, and skip the last sc before ending/joining