It was always 1 kill for Scout or Defender (to encourage more to choose this path) and Berserker path flexed depending how full the Villlage was.
A rough guide was:
Less than 10 members = 1 mage kill for Berserker
10-15 = 3 kills
16+ = potentially 5 or more, depending how many berserkers we had.
I would induct Berserker wannabes after 1 kill, they just couldn't choose the Berserker path until they had their kills. This at least gave them resist, spellbane and access to the Village. Which at low ranks makes you tough enough.
Not sure if this is still the case, it is very much upto the Commander with some guidance from above.