Our wizard goes to spend his quest reward to buy an expensive looking wand (because he was from a rich family).
At the shop, the rogue is caught shoplifting and the shopkeeper calls guards, so we have an unexpected encounter.
The wizard has already acquired the new wand. Can he use the newly acquired wand right away, or does he need to attune to the wand first?
The answer ideally should cover not only arcane focus, but also holy symbol, druidic focus, and such.
Related question, but not a duplicate since the focus in question is already complete/perfect: Crafting an Improvised Spellcasting Focus? and Using an Improvised Spellcasting Focus