depends how cold it is. on road bike a good base layer for legs and body and roubaix bib tights, winter cycling top, couple of buffs, winter cycling boots and i feel toasty to about minus 10. for mtb then the same although with a pair of baggies over top to give the lycra a bit of protection.
only thing i really feel the cold with is my finger below about 5 degrees i struggle with keeping my fingers warm no matter how much i spend on quality gloves and undergloves.