Just do it, go to the gym, alot.
Definetly dont ski till 6 months even if your knee feels stable and strong, the donor acl ligament gets progressively weaker in the first 2 months after surgery(this is your donor hamstring tendon dieing), then around this point begins to replace your dead hamstring donor ligament with new tissue(your new acl), it'll do that for the next 10-12 months. If you had a meniscus tear too, that just adds to the risk of wrecking your knee again.