It is very clear that early-game, buying things is not a viable option anymore. Given the lower natural GPT you get, and how buildings and units still do cost GPT, it's made evident that building a worker right off the bat is needed, and early expansion is a must. Worker-Settler is a good course of action even for otherwise tall-oriented civs that would go for scouting or making Monuments and Shrines. You absolutely need a high concentration of luxury resources, even if they're copies or not viable to improve yet, to get your GPT up so you can do pretty much anything. Jumping on caravans and cargo ships is a must- while before, you could get away with avoiding Animal Husbandry and Sailing for a while, that's not the case anymore. Trying for the Great Library jump to Philosophy and the National College isn't something you can casually do, as going in that direction could leave you crippled compared to others early on in the economic department, and you'll have less capacity to do much more from there, like buildings or more units.
Of course, this leaves Songhai with a massively bumped up early game. Hell, out of everyone, they basically have the most freedom to do what they want from the start, as that gold from encampments is an empowering fortune when you and everyone else is making 2-3 GPT on a good day. They can afford to be in the red for a bit and bump up military or infrastructure, because their cushion of gold means they won't be at the goose-egg for a long while.
Conversely, early aggressors and those with Ancient-era UUs are very nerfed. The Huns and Carthage especially have fallen down, since swarms of Battering Rams and Horse Archers are limited until opponents have the defenses to deal with those, and Carthage...ooph. That loss of Production is brutal, and good luck getting Quinquiremes out en masse while they're still effective. But then, they probably have to be played more for trade now, and Quinquiremes used to defend cargo ships instead of attack cities. If anything, the African Forest Elephant is a bit more attractive now, since selling off Strategic Resources early on can make the difference between bankruptcy and prosperity, and hooking up Horses can net you some gold while still giving you a tanky mounted unit.
Early warfare is even more limited now, which means going for that requires either supreme efficiency in getting units out there while your opponents are still weak and using them strategically instead of rushing, or setting up your own economic infrastructure as fast as possible to afford a greater volume of units. The Inca are especially dangerous with this, since they can set up roads without GPT cost and go for long distance trade routes early on when for everyone else even two road tiles would make the available trade routes a net loss. I already notice Pachacuti pumps out a massive amount of military early-game, but the expansion means he's capable of keeping that up when everyone else is less capable of defense.