Building on what Henroo said,
Grounds of the Orc Strategists (gotos) is the only way (that I know of) to get Orc Strategists before Chapter 8.
You just need to place it in the city, and it will produce the units automatically every 6 hours. Similar to the residence, mechanics-wise.
I built gotos (and valorian valor) every time it is available in the magic academy, and I had 5 of them when I reached Chapter 8.
I would build new gotos and replace the old ones when I reach a new chapter, rather than using royal restorations.
Playing as Human, Orc Strategists is an excellent troop against light range units.
Barbarian is not that strong, and Mortar is very fragile.