This AOE2 Scouts into Skirmishers build order is a standard scout rush build order that expands further and adds skirmishers to the army. You can find this build order in the Cicero build order mod. The reason for doing this is mainly to counter and spearmen that the opponent is using to counter your scouts. If you have had a good initial scout rush, you should have made your opponent panic and make lots of spears and hopefully killed some of his villagers.
This justifies adding skirmishers because you would have slowed down you opponent from reaching the castle age and gives you an opportunity to inflict more damage to their economy once the spearmen have been dealt with by the skirmishers. The skirmishers can also add weight in to the attack of the villagers. If your enemy has walled around his villager collecting resources, the skirmishers give a great opportunity to attack those that your scouts cannot reach. This can be a really strong feudal age strategy but is one that tends to be under-used.
The AOE2 Scouts into Skirmishers build order is as follows:-
Dark Age
6 vills to sheep 3 to wood (with LC) 1 boar 1 build 2 houses then berries 3 berries 1 2nd boar 2 boar, move weak villagers to farms 3 wood with 2nd lumber camp Loom Click up
Whilst Advancing
As soon as you click up, send 4 villagers from sheep to wood (5 in total per lumber camp) when feudal age is half way completed, make a barracks with a wood villager.
Feudal Age
Make a stable once Feudal age comes in and research double bit axe and horse collar make 3-5 new scouts all new villagers to farms (total 10-14 farms) make range and make skirmishers send 4 or 5 new villagers to gold