How to join a Clubhouse quickly

If any of your friends use the Clubhouse, you can check if you are in his or her address book (if not, ask for registration in your address book) and apply for subscription by installing the app.  Then, even if you don't have an invitation, you can sign up with a high probability.  

First, you must have yourself in your acquaintance's address book.  I'm not sure how much time it takes to register in the address book and enter the clubhouse.  

I just signed up for the person in my address book more than I signed up for the invitation. It seems that the notification appears only when the existing subscriber says 'very frequency' in the setting.