Make sure you don't have any Xbox live gold or current running subscriptions.
Purchase one two or three years of Xbox live gold cards from GameStop or Walmart or somewhere.
Enter in all the codes don't accept any extra or free months of gold you cannot go over 3 year or it won't work.
Now this is important you must not have any current subscriptions other than gold you cannot have pre-existing ultimate or any of that happening it needs to all be expired.
So after you have confirmed that you have no more than 3 years of Xbox live gold with no other subscriptions pay for one single month of game pass ultimate. Every month that you have of existing gold will instantly be converted into ultimate.
Turn off reoccurring subscriptions now you just got 3 years of ultimate for 180$