Esperanto webpages and blogs speak of "local groups" and "clubs." I don't know what the difference is but I have an opinion on the ideal size for a group of learners.
The principles of managing a large group differ from a small group. There are four basic sizes for groups (but only the first two are relevant to us.)
1. Face-to-face group. Effectiveness diminishes if there ae more than seven members.
2. A group of 8 to 17 members can benefit from the advantages of a smaller group, providing the members are well-acquainted with each other and see each other at least once or twice a week.
This is the common size for the basic unit in a military organization. The value of this size is illustrated by the nine players on a baseball team, the eleven players on a USA football team, or the basketball squad that usually includes from 9 t 12 players.
It is also the size of a typical chuch choir, women's circle, high school youth group, or active members in a book study group.
Most people can keep track of only 15 or 16 people in our head, recall their names without hesitation, and relate to comfortably.
The disadvantage of a group this large is that it is possible for someone to be absent without being noticed, and it is difficult for everyone to be able to have an active role in discussion. (If each person speaks for only two minutes at a time, a participant can speak only four times in a two-hour meeting with 15 participants.)
3. 35 to 40 participants is as large as a group can be with the relationship of the members as the basic organizing principle.
4. More than 35 to 40 participants require large group management methods.
In my opinion, too many small Esperanto groups try too soon to use methods suitable only for larger groups. There is no need for groups less than 35 members to make a constitution and by-laws; that will ruin what effectiveness they have. On the other hand, a large group cannot use small group methods.
Small group management techniques to strengthen cohesion include use of the circle as the basic seating arrangement, asking participants to take a minute to introduce themsleves to the entire group, and encouraging everyone to relate to every other member.
It is obvious that if there are five members plus a leader, if the meeting lasts one hour, every person can only speak for a total of 10 minutes each.
I believe if a group exceeds 4 members, it should split into two groups, etc.
I myself recruit and mentor only individuals, but I've dealt here with group dynamics for the benefit of those of you who will work in that manner.