Danerys's next move?
Okay, she's destroyed Cersei's land army.
The logical next step should be to tell the Dothraki to get the Unsullied out of Casterly Rock and to loot the Westerlands on the way, and take all three dragons and go looking for Euron's fleet. Which are all nade of nice flammable wood.
That would leave Cersei with no army or navy or food coming into King's Landing, the smallfolk there will probably be ready to mail Cersei's head to Dragonstone in a couple of weeks.