If you can add real telegram users please reach me via PM. I don't want bots, i mean real users from another group.
Why not create a campaign to join your group for 0.5 dollar (BTC) and pay with the lightning network? You can ask members from Member+ to join your group and thus ensure that no one will leave the group after receiving payments.
This is one of the ideal ways to get real followers, but it is better to provide excellent content to encourage others to join your group rather than paying you.
Note [1]: I dont know if this violates BTT forum rules, but I see that it happens with Twitter.
Note [2]: I am not sure if this breaks Telegram's TOS.