...from just before attacking Shaka. I'm not sure if this is the most ilustrative, but it's obviously the key moment as once I took Shaka's land I had a strong enough production base to take on Toku.
The key points were:
1) early diplo to befriend Ragnar (Shaka went WHEOOHRN before I could do anything);
2) knowing Shaka would attack and preparing a defensive stack in a walled hill city;
3) settled representation super-specialists in a wonderspammed capital for research;
4) pacifism for most of the game to get more GPP;
5) small empire which allows high slider due to low maintenance;
6) enough cities to get the globe and draft in a strong food site;
7) Steel from Liberalism and building cannon in the capital
I never bribed anybody to war. Bribed a few people to peace though, as Toku really kicked Shaka's ass and the latter would have capitulated. I got pretty lucky, Shaka was under a lot of pressure, lost cities, and at the point of this save is under attack again from Toku (had to bribe him out a second time) and Ragnar, so the timing was perfect. If that hadn't happened I would have attacked a little later with more rifles.
If there's anything else you want to know or if you'd like to see any other saves, just ask.
I finished it by the way. Killed Genghis and waited for border pops. I was then about .1 of a percentage short in land %.
The problem was that Alex still had a city in formerly Mongol lands, so I prepared to attack him and his master Ragnar. I also turned up the culture slider, though, and just before I was about to attack I won peacefully from flipping a tile somewhere.
Notice my stack about to strike.
And the inevitable unimpressive late-game score: