I can't tell what your hair properties are by looking at them, but it looks like you have a 3B curl pattern.

Most anti frizz serums are chock full of -cones, so that might not be a route you want to go down. A good leave-in (for me the better the moisture the more lacking the frizz) with a gel that works for you will probably work. Plopping while your hair is wet might also keep the water from stretching your curl so it retains shape without gel.