At least one 20A branch circuit for laundry room receptacles only. – 210.11(C)(2)
Washer: The receptacle for the washer can be put on the laundry room circuit.
Dryer Gas: The receptacle for the gas dryer can be put on the laundry room circuit.
Dryer Electric: This circuit should not be smaller than a 30 Amp line (Run a 10/3 wire for a 4 prong receptacle). However, a larger dryer would require a larger wire size.