You either:
- Are lucky and the game puts you in a good levelled crew when you start
- Are lucky and have a friend that can invite you
- Are lucky and while playing you randomly get invited by people in online lobbies
Or
- You need to put some effort into actively searching for someone to invite you
I did this in public lobbies, simply go in the menu
and press
the players list will pop up, check the crew tags and if in your lobby there is a leader, admin or recruiter of a lvl 50 crew, message/add him. If you're lucky, you'll find some nice guy that will accept you in his crew. Just search up his crew's name and request to be added.