Assuming we're not collaborating battles and we fight each other? If we have at the minimum of five players, two characters each all level 1, that's ten avatars that can fight each other. Assuming that there's a winning streak, it'll take 27 duels to reach level 9. Now if each player takes about three posts each per fight, we're looking at 169 posts for each level 1 player to hit level nine, assuming that they're on a constant win streak. That's only including duels between the players, not any NPC avatars or missions. Also I did not include if the players were powerleveling on the same character or not, which may skew the results to a greater degree. May be greater or shorter depending on if we collaborate for each duel.