Also, in case you're wondering how you can come to these conclusions yourself. I would try to weigh the value I can extract from all the things I can produce now (e.g. settler, builder, monument) as well as the cost of producing said things. A builder has maximum utility when you can expect to expend all its charges as soon as the builder is produced AND you can immediately start benefiting from the tiles improved by the builder. A builder has low value if all you can use it is to build farms on naked flat tiles. If you can improve wheat, horses and diamond, you're getting a lot of value because you're getting three eurekas and an inspiration for a civic you typically want to boost very early, and you're also getting a strategic resource and a luxury, both of which you could sell to the AI for a lot of early-game gold. The value of a monument is the 2 culture per turn it provides, but early-game, you may not actually get the full value of 2 culture per turn because you might end up wasting some culture by being forced to unlock civics that you can easily boost before you can boost them. Getting a settler out before a monument typically increases the value of the monument because it's easier to boost Early Empire with two cities than one since it's much more difficult to grow your capital to 6 pop than to grow it to just 4 pop and the 2nd city to 2 pop. Early Empire unlocks Colonization, which lowers the cost of producing your next settler. You can kind of see why it's usually a good idea to produce your 2nd settler as early as you can.