This trophy can be seen as confusing, as “rare” equipment to many early-on in the game might mean unidentified (UNID) equipment that are found in chests in Vellgander or as reward box items and require appraisal at a merchant. In actuality for this trophy, it is collecting one-piece of Guild Rank (GR) 26 equipment. These can be seen and binded at a binding shop once you reach Binding Rank 19. Also some GR26 equipment can bought with Dahlia currency at an adventurer’s guild merchant.
Getting to Binding Rank 19+ can be done as you work towards the binding trophies. Donating items, especially your excess Guardian and Chromium Gems contribute the most value to increasing your binding rank.