Each Wizard's Arcane Tradition subclass gives them a "Savant" feature:
Beginning when you select this school at 2nd level, the gold and time you must spend to copy a [school] spell into your spellbook is halved.
As well as one or more features that affect or are affected by spells of that school of magic, such as in the School of Conjuration's Benign Transposition:
Starting at 6th level, you can use your action to teleport up to 30 feet to an unoccupied space that you can see. Alternatively, you can choose a space within range that is occupied by a Small or Medium creature. If that creature is willing, you both teleport, swapping places.
Once you use this feature, you can't use it again until you finish a long rest or you cast a conjuration spell of 1st level or higher.
Wizards learn two new spells every time they level up, and they can also copy spells they find into their spellbook (for a cost of gold and time).
My question is: Is it generally more effective (cost/efficiency-wise) for a Wizard to learn spells of their chosen School at level up (to gain access to spells that benefit their subclass features sooner) or to copy them from spell scrolls or other spellbooks later, for a reduced cost?