A few Questions

You don't need 5 slots, but serious competitive teams will probably not accept you if you have less. Furthermore, you can't join a competing team mid-month (as tournament registrations have already ended by then) and expect to play in the tournament.

However, you'd be able to join a team anyway, but you'd be limited to playing practice matches -- which you will need, and will be grateful for. The competing teams are usually composed of kickass veteran players and are highly, highly skilled.

If you've got a Discord account, head over to the official server and ask around in the appropriate recruitment channel to get yourself a team.

That said, welcome to 6PL!