Dungeon Sets:Massive coverage of standard linear wall types! Upto 14sqft for as little at $0.14/sqin.
Castle Sets:Massive coverage with a large variety of wall types, including oblong! Upto 14sqft across multiple levels, for as little at $0.15/sqin.
There is only roughly 5% of large piece type overlap between the Dungeon and Castle Sets, so they greatly expand each other! Pick one set up, then pick up another set type up later for huge capability gains!