We love to be in the numerical minority.
Being in a group of several million among hundred million feels great. So does being in a group of a hundred among a thousand, and a group of ten among a hundred. You feel a unique sense of connection with one another.
We love to support an underdog. It makes sense to position the group in the statistical minority, as the underdog, with big goals requiring commitment from members to achieve.
The mistake we often make is claiming to be the biggest, best, most successful group in our field. You want to carve out a unique group among your audience.
We also love to associate our own identities with groups that have momentum. That's the bandwagon effect in practice. We derive our own identities from the groups we belong to. We can raise our self-esteem by associating ourselves with successful groups (and disassociating ourselves from groups that don't seem successful).
So position your group as the underdog with momentum.