Generally speaking Horseback Riding (HBR) has some bugs and it’s best to keep your HBR below your archery skill level so your ballistas don’t commit suicide. There is a bug where your ballistas might keep moving forward in battle instead of stopping to shoot. If your archery is 8 for example you want your HBR to be 7 or below. You do not want your HBR to be as high as your archery. I’ve lost 800 ballistas when attacking NPCs that I should have easily beaten and I’ve seen my friend lose 1200 because of this bug.
At certain levels barracks are more important than others.
Level 1 barracks make workers and warriors.
Level 2 barracks make scouts and pikemen.
Level 3 barracks make swordsmen.
Level 4 barracks make archers. ALL your barracks should be at least level 4 so they can make archers. Archers are the most important troop in the game.
Level 5 barracks are used for making cavalry.
Level 6 barracks are used for creating transporters.
Level 7 barracks are used for making cataphracts.
Level 8 barracks are useless. They make no new troops. So no need to have level 8 barracks unless you’re making level 9 or 10 barracks.
Level 9 barracks are used for making ballistas and battering rams.
Level 10 barracks require a michelangelo script. They can make catapults. Catapults also require a level 10 forge.
I usually make barracks up to level 4, level 6, or level 9. There is very little advantage in having barracks at levels 5, 7, or 8.
Ballistas work great on NPC towns but not so great on players. In fact there is an advanced strategy for attacking NPC towns without any losses at all. This strategy requires ballistas and transporters. I find I use my ballistas and transporters a lot of fighting barbarians but I don’t use them at all when attacking players.