The early game is a tension between three factors: Scouting afar to collect goody huts, meet city states, and discover continents and wonders Building military to defend against barbarians / AI rushes and to scout nearby terrain Developing your city and/or expanding But given the high value on expanding, the solution tends to converge to the point where you do the bare minimum amount of investment into the first two factors (or even less than that!) so as to develop your empire as quickly as possible. (or, to overdo the second point with an eye to conquering your neighbors so the investment doesn't go wasted) For example, some people have already decided never to build a scout, preferring instead to build slingers (or warriors) to do their initial scouting and pull them back to defend and/or clear barb camps. However, the ability to sell units for gold means the cost of investing in the first two factors isn't as much as it immediately seems. Recall that, at least on default settings, you can buy a unit or building at a price of 4 gold per cog, and you can sell at a price of 2 gold per cog. Thus, building a unit and then selling it again "wastes" only half of the resources that went into it. (assuming you can effectively use gold purchasing in your opening) For example, one could consider building their scout to scout afar, and later selling it to purchase a their second builder or a infrastructure building. Or building an extra slinger/warrior and clearing all of the nearby barbarian encampments, and selling them to buy infrastructure once the terrain is secured they're no longer needed.