Bottle nipples

Hey ladies. Have been trying to start putting things on my registry. Was adding bottles. We've decided to go with the Avent Natural bottles. Put a few on there (3 sets of 3 bottles each...enough??) but I figured I should maybe add some extra nipples on there too, but I see there are different flows. Do I need to register for extras on all of them??? Which do you think are most used? Fast flow, medium flow, slow flow or newborn. 4oz bottles come with newborn flow, 9oz come with slow flow and 11oz come with slow flow as well. Should I just get the medium and fast flows? Thanks in advance