Two kinds of items
Blue Prince items split into two groups. Permanent resources stick with you across days and slowly change what the house can do. One-day tools help within a single run and reset with the manor.
Knowing which is which changes how you draft. A permanent resource is worth a detour every time; a one-day tool is only worth it if today’s route needs it.
Reading the item list
The item database holds 70 items, each with a description and, where the wiki lists one, a location. Filter to items that list a location when you are hunting something specific.
Which items matter
Route around items that open a room or a puzzle. Keys and special items are the ones worth shaping a draft to reach; the rest fill in once the path is open.
When you are stuck on a lock, check the item list for what opens it before you spend steps brute-forcing the wrong wing.