What you have written is exactly what people would say ; you don't need 'ones'.

The way that you have it written is correct. "Ones" is usually used if you're pointing at something specific but don't know what it's called. For example, if you wanted the cinnamon bagels but didn't know what type of bagel it was, you could say, "Put in two more blueberry, two more onion and three more of 'those ones' [then point to the bagels that you want]." You could also just say "three more of those" and leave out "ones," but saying "those ones" is a bit of a habbit for many people when they're selecting from a wide variety of choices. Hope that helps!