Fastest way is House of Crom. Inconceivable set is for bear there and you can get half of it easily from Threshold of Divinity. Other half is in Vile Nativity and a lot harder to get.
Khitai dungeons is next fastest way. Just take whatever medium armor drops from random normal modes until you're fully in blues. If you have friends who can get you through hardmodes (esp Karakorum), you'll be decked in blues (and a few pinks) in no time.
Khitai faction questing is slower, but not too slow. Probably your best bet if you don't have friends for dungeons.
Raiding is the slowest way of gearing up but it'll all be pinks.