Your coaches should be able to teach you everything you need to know. I joined the team a week before the first match and ended up playing in it because it's so easy to learn. That being said, all the rugby specific workouts will most likely be covered in practice.
90% of our drills include: passing drills, tackling drills, and just scrimmaging. Since you can't do that on your own, I'd just suggest you do some HIIT training (mimics the game play style of rugby); and do squats, cleans, and deadlifts to build speed and explosiveness.