The most popular builds for d/p are 2/6/6 and 2/6/0/0/6. For d/d its 2/6/6.
If you’re new to the thief class I would stay with 2/6/6 until you feel you can kill opponents quickly. 2/6/6 will give you condition mitigation and some training wheels in case you mess up. Once you feel comfortable you can try to see if the all-out-offensive 2/6/0/0/6 is right for you. You’ll do more damage but you’re also very squishy and vulnerable if you can’t keep your opponent blind.
Try running these builds in PvP just to get a lot of practice in a short amount of time.