Try half a ml and work your way up.
Allow multiple hours to pass before redosing.
Also, it is important to understand that the magnitude of the effects accumulate in a nonlinear fashion.
Meaning, the effects of 2ml may not feel like its "twice as strong as 1ml" as one would expect, but rather 3x stronger, or etc. This especially true with repeat dosing. One might be having a fine time, being modestly inebriated from previous doses, then get hit with unexpectedly severe intoxication when 1ml more is added.
So basically, it's fairly unpredictable stuff and easy to wind up much more fucked up than you wanted to be. So becareful. It's easy to go from "hey I barely feel much of anything" to "I feel horrible, please make this end"