Your level is based on how many likes you have.
The only rule is:
The monsters depend on the highest person level, unless going to a lower level'd dungeon (by saying so)
Example:
(Level 52) Noob: I would go to a high level dungeon and farm items and xp with you
(Level 6,531) Fatloser21: I'd force this kid to grind with me to gain some fast levels
(Level 5,212) Coolloser22: I'd make him cook for me
(level 4,211) Kid: I'd kill him and take his stuff.
You don't have to say your level, just makes explaining it a lot easier.