Gold and gambling
Gamble for high-level uniques
Spend accumulated gold on random equipment offers when your character can access the item tier you want.
Town gambling vendor.
Repeat whenever farming has rebuilt a discretionary gold reserve. The results remain random, and each purchase spends gold.
Stop gambling when the next purchase would compromise map access or when the gear slot has no likely upgrade; resume after earning more gold or progressing to a higher tier.
Open a guide to find other locations and see what the item is used for.
Spend accumulated gold on random equipment offers when your character can access the item tier you want.