[White Morphin Ranger]

I believe Zordon was the leader of the group, and the Red or White Ranger were always the "field leaders." Like the X-Men. Cyclops is the field leader but Professor X makes most of the calls.

Anyway, to answer your question about the favorite ally, since Zordon was as much a part of the Ranger team as any of the "normal" Rangers were, I'd have to say Magna Defender. He was the sixth HERO on the show but not the sixth Ranger. His powers were never said to be related to the Galaxy powers. This is further implied by the fact that Torozord never combined with the Galaxy Zords.