It's different for everybody.
I have a prescription & its for half a mg. I'm fine on that. Just make sure not to mix with anything else as it intensifies the relaxed feeling which can turn into sleepy & slurry.
I used to need it at least three times a week so I wouldnt go off the deep end. But working through my problems with a therapist & taking cymbalta daily have fixed me up pretty good! I don't even take ativan anymore unless I fly... MAYBE??
Good luck to you