In all honesty, I think that the best course of action for tourettes and other types of stimming (like Asperger's) regarding marijuana is to take it for a week/few days on, same off, over a number of months. This will possibly allow your body to develop methods and thought processes to divert such tics. Plus, you might even enjoy the buzz.
Myself, I have used marijuana for multiple years with various results, and through experience I can suggest a number of things you might want to consider, like:
-strains of cannabis, and sativa/indica considerations
-mental addictions, and your resistance to them
-mental stability, as using marijuana might cause you to panic or become paranoid after extended usage
-social understanding of other, and your own involvement
-method of consumption
-and if necessary, say there's a trait you don't agree with, just how much you're willing to burn/digest/vaporize/absorb into your skin (there's creams available at legal dispensaries), or if it's the right method of treatment for yourself.
These are all difficult decisions, and it is just as likely to make it worse as better if you abuse your intake. Rest assured though, there is no measure that is too much for the human body to keel over with, as you would pass out long before you could ingest or inhale enough considering the current methods of consumption are limited. Nobody has died yet to an overdose that is known of, unless there is a possibly of an allergy (over a hundred die from peanuts a year, for comparison...damn you Mr. Peanut!!!).