All of that takes time. You can negotiate GE4 your first week on a new world. And if a new Iron Age city can muster the goods, a further along city with more space, some event buildings, etc certainly can. And negotiating never gets any harder. The multiplier on goods you pay is the same in iron age as it is in SAJM - your city just makes more
Fighting will usually be the goal, but if you want to do GE4 *now*, you negotiate while you work on that. And the start of a new world is when you might actually care about those GE rewards
(Of course with my luck so far on Dilmun that's not exactly a great advertisement - 4 GE4s in I have 1 Level 2 Face built lol. I have a Terrace Farm upgrade but not Terrace Farm *to* upgrade) ; but I've had other worlds that had great benefits from early GE4