So you spend the gold on buildings instead, or on alliances with select CSes? You're right about the Abbassids, I was going to mention them.
Buildings, mostly, with the cash from Persia thrown at Abbassids to facilitate crushing Arabia. You might be able to set the Crusader States against them too but they are marginal allies at best.
You can't raze capitals and you really aren't going to make enough Scouts and back-fill units out of your capital without some support. I usually Colosseum + Courthouse the capital of each defeated Civ when I have the funds and use them to push out extra bits and pieces by micromanaging them - like extra scouts or a random cannon.
What did you do on your walkthrough? How quickly did you take out each civ? I know you mentioned you took out both Chinas around turn 50?
I killed Ulghar first, after upgrading 2 Keshiks and sending one Horseman on a Grand Tour to get City State gold and trade contacts with other Civs. My workers chop-rushed to help me build infrastructure, then built a sheep pasture and some farms, then started in on connecting the capital to the Silk Road. I finished the Honor tree with my Turn 5 policy and the Cultural CS bonus. I trade away extra horses and iron to Wu for Gold, then DoW'd her, provoking Western Xia into warring on me. I stomped a mud hole in them and got bonus Horsemen and gold that I converted into more Keshiks.
At this point the Song / Jin conflict had drained both sides and they sued for peace with each other. I stomped Wu's Western city, taking Spice and Silk. Then I went after her southern city for Pearls. At that point she offers one of those capitulation Peace Treaties, giving me all her cities but her capital. I accept, raze the useless city, and reposition all my forces near Beijing.
I'd resold my resources to Jin slightly earlier for gold, so my DoW wipes out those deals so I can resell to Persia or Russia (I think Russia was more warmonger tolerant so I got better deals with Cathy). Beijing went down quickly when attacked across the hills from its North West. That takes out the Great Wall penalties that Jin tries to use to stop your hit-and-run. Then I went East and razed the city nearest Korea. The rest was mop-up.
Wu's last city is completely overwhelmed. It is just around turn 50 and I'm catching a good stride. Beijing and Shanghai get Courthouse / Colosseum and are tasked with building infrastructure or scouts while the Mongol capital is pumping out scouts like made to garrison every city for happiness.
Take everyone on the road to Persia. Violence ensues. I burn down two of Darius's cities, back-fill garrisons with scouts, and buy out Abbassids. I move into some neutral territory in the what would be modern Saudia Arabia, then DoW Arabia and stomp out Mecca. From there you can swim across the Red Sea and beat down Cairo, and then go up to Damascus and whatever their last city was.
Byzantium only has 2 cities, and only one of them puts up a real fight - Constantinople. The terrain approaching it kind of sucks. Hopefully we have some back-filled cannons and cannon-fodder (musketmen) at this point, as well as some Keshiks with Siege, Logistics, and Range.
Punch through that and Russia is cake so long as you hit her troops first, then her capital. Don't get caught up in a 3-way crossfire at the hub or her roads or hung up on the forests and marshes.
That finishes an Emperor run with minimal complications within the time limits. Gandhi and Nobunaga aren't maneuverable or brave enough to challenge you outside of their own territory, and the other Civs pretty much can't gang up on you outside of China due to their placements.
- Marty Lund