A 'treasury' is defined as:
1a : a place in which stores of wealth are kept
b : the place of deposit and disbursement of collected funds
especially : one where public revenues are deposited, kept, and disbursed
c : funds kept in such a depository
a : a governmental department in charge of finances and especially the collection, management, and expenditure of public revenues
b : the building in which the business of such a governmental department is transacted
3 capitalized : a government security (such as a note or bill) issued by the Treasury
4 : a repository for treasures
And a 'journey' is to travel from from place to another; a trip.
So your sentence roughly equates to "My trip to the bank where wealth and treasures are stored," or "My trip to the finance department."
'Treasured' means something that you hold or keep as precious; something you cherish. "My treasured journey." = "A trip that was precious to me."
'Treasure' - something of great value; wealth; a collection of precious things. "My treasure journey" = "My trip to find treasure."