Azura cruise only use pounds as currency and you can have your dollars or other currency converted at the ship's money exchanging counter. Tips for the stewards at the Freedom Dining are pegged at £1.60 per day. This amount is automatically charged to your account so you need not pay your waiter directly. At the Dining Club, they do not automatically charge the tip to your account so you have the option to give more than £1.60 each to your waiter and assistant waiter. As for the cabin stewards, the standard tips are at £1.50 per day but you have the option to give your cabin attendant more if you want to.
For more info, see Azura Cruise Ship