Testie,
Riverside Grasshill > Plains hills. Always mine grass hills first, especially riverside.
I would not panic about Khmer. Grab that wheat cow spot, then the horses. The rest of the land is crap up there anyway. Hopefully some seafood pops up around that flood plain to the west.
For the horses, if you were creative, I would settle on the river with expectation of getting those sugars, but I'd settle next to the horses immediately. It's a resource grab city, but at least you can farm it and have sugars later.
Question is, are you isolated with Khmer. Weird to see only 2 civs on a continent. Something may be weird. Make sure you scout the south coast closely.
Bang out another worker. Use both to road to the new city and improve it. (note, if you settle a city after completing the route, even on the same turn, the city will get an instant trade route. If you settle then complete the road that turn, then no trade route.) Cap can build another warrior or 2 and start on settler 3.
You might want to pick up Myst first before heading to Writing to get border pops, since you are not Kublai.
edit: try to send a warrior out asap to the new city site to spawnbust...you should have done that earlier.