Civilization has many variables which should have interesting "synergies," but usually I find halfway through that the synergies don't pan out.

So here are a few.

Iroquois and forest-roads. The idea is to keep the Iroquois territory wooded and connected to other Iroquois cities. Especially with Liberty and the early settler.

why it doesn't work: the tile only works as a road if it is within your cultural boundaries. So you're going to be happiness or gold locked anyways, as new luxury resources to alleviate unhappiness are usually far apart geographcially. And since I at least build my cities far apart, I'll not have the gold for buying the tiles

The liberty tree in general. It's supposed to give you an early and fast settler. But since you're happiness/gold locked, it doesn't really work out.

And the early settler is located 3 down the liberty tree, making it too inconvenient. The tradition tree is much better.

and it's late, and I'm irritated at this game.