if you get 2 then ideally youll want 2 females. you cant tell their sex until they are about 18 months old though. you cant keep 2 unknowns together really until they are sexually mature. il be splitting my 3 up very shortly.
youre better to get 1 for now and then add another when its older.
have a look at Care of The Chinese Water Dragon lizard (enclosure, diet, health, illness, temp, heat, humidity, cage, vivarium, terrarium) for heating and lighting info. its easier than me typing out the same stuff.