The new
Armorsmith is also really nice to be able to make 5 star armor sets - the
Iron Quarry built early shouldn't be disposed of (Edit: too early) because you'll need lots of Copper Ores (200 per equip). And you need them with the correct suffix (e.g. Might) and/or good stats if you're a perfectionist so it'll take many Copper Ores.
Edit: Building a
Salvage Yard seems like the better choice! Thanks to Nightingale.
Small plots provides for many buildings that gives passive income/buffs which is the most useful throughout the game, don't waste it on Iron Quarry just for copper ores. Salvage yard is more resourceful in breaking down equipments for more copper ores in addition to other materials of all rarity that can help in crafting high tier equipments in the Armorsmith.
If you cannot clear up to the Legendary 4th Act (because the materials you need to make the equips are there) which many players (I'm assuming) will have trouble with, as the Gryphon Lord at Legendary 3rd Act's final map is quite a huge hurdle to overcome; you can build
Fusion Altar to acquire the materials needed!