How can i farm currency in Campaign?

I am at the end of Act 3, and i want to know how to farm Exalted orbs, i just had 15 of them till now got most of them through regal shards, almost used all of it to upgrade gear as i feel like i am reaching a ceiling and cant move forwards without getting health and resistance on my gear! Is there an efficient way to farm it in campaign or do they drop more often in end game? Like whats the catch to farm them ? And when/where to farm them? I want to try crafting gear but the lack of resources is just locking me down to low level gear which is all approx 20-30 levels lower !