Building Time Reduction Boosts

Gear - 61.60%
Boots & Crown of Abundance

Gear Type	Gear	Boost	Lord	Gear Cost [steel]	Materials
		Speed	Level
Greaves	Boots of Abundance (Golden)	30.80%	21	101K	4800 Animal Hide,  4800 Pine,  1 Dragon Hide,  1 Enchanted Crystal
Helmet	Crown of Abundance (Golden)	30.80%	21	101K	7200 Bronze,  2400 Pine,  1 Dragon Hide,  1 Dragon Bone
Total		61.60%	21	201K	7200 Bronze
					7200 Pine
					4800 Animal Hide
					2 Dragon Hide
					1 Dragon Bone
					1 Enchanted Crystal

Alternatively, you can pick up a fairly cheap gear that will provide a -35% boost
Galahads Boots & Dawn Cornet, from the alchemist corner 

Relic - 15%
Relic holder - Hammer of Time

Temp Relic - 20%

Individual Store - Craftsman's Hammer

Temp Talent - 20%

Individual Development 5 minute talent boost [Activate last]

Age of Development - 20%

King Activation

Building Booster - 20%

Alliance Spell

Research Construction 1 & 2 - 25%

Economic Talent points [Require 188 points] - 15%

Requires a Talent reset

Heroes [4 Star Heroes] - 27.50%/23%

Heroes [4 Star Heroes] - 27.50%/23%

Gear - 61.60%/35%

Relic - 15%

Temp Relic - 20%

Temp Talent - 20%

Age of Development - 20%

Building Booster - 20%

Research Construction 1 & 2 - 25%

Economic Talent points [Require 188 points] - 15%

Possible Construction speed Up Boost - 224.1%/193%