Knowledge of giftedness is, IMO, not at all important. You’ll need a bright therapist who can run with you, though.
What is important, in my experience, is the therapist’s openness to new ideas, understanding of the experience of being an outlier, and a good therapeutic alliance. Therapists who work with patients with terminal diseases or disabilities have a special gift in understanding the outlier component, I’ve found.
I also tend to look at the list of therapeutic models they employ, but that comes from knowing how my particular mind works best.
You won’t regret therapy! Personally, I think it’s a lifelong investment in good health, and it is a superb prophylactic against unhealthy habits.
