This time, we had some troubles to arrange the thing with the skipasses. The best and cheapest option was, that you book your skipass on your own via the website of the Dolomiti-Superski 3 days before arrival. If you do so, most of you will get a 5% discount. The same would also apply for group-bookings, but then we would have to pay for organisational stuff e.g. the travel agency.
At least two days before you start skiing (I would do it a week before arrival), you can book your skipass online. If it is more than just one day for skiing, you will gain the mentioned discount of 5%!
After payment/checkout you will receive an e-mail with a QR-code. With this QR-code you could print your final skipass at the machines they have nowadays at the valley stations. Just scan the code, and the skipass gets printed.
IMPORTANT: on booking select "in the whole dolomiti superski" at the very first step, to make sure you can do the Sella-Ronda!
English website: https://shop.dolomitisuperski.com/home.aspx?idlang=en
German website: https://shop.dolomitisuperski.com/home.aspx?idlang=de