Ya, TEATRC needs more ladders.
Personally, if I do join a realm it's usually the Laurians, since their "Don't give a ****, conquer ****, no ****" attitude is rather appealing to me. Just get some pikes and arquebuses together, stand together in a proper formation, and make holes in people. Add some assimilated specialists for flavouring and the whole thing is a solid and economically supremely supportable concept. Get some footmen, train them only one single tier higher, free some prisoners on the way and just keep rolling.
Going up against the haelmarians? Hackapells and lousy infantry, so grap more pikes and get stabby! It's the swadians? An equal mix, pikes to stop their heavy cavalry and arquebuses to outshoot their "sharp"shooters. The ****ing Kaiser? Take whatever to the field and throw it at them, those prussian boneheads never knew how to handle the unknown. Vaegir? Guns! Guns! More guns! And down they go!
And if ever you are outmatched, quickly upgrade your units to top-tier (which they'll all be eligible for by now), and watch the enemy run into pointy stuff.
Seriously. With Laurians, it's all about being aware of how ridiculously cheap and easy it is to adapt. The swadians may have better pikes, and the haelmarian musketeers outshoot us, and ****, what's cavalry ever good for? But most enemies have weaknesses, and those are easy to exploit.
Ah, and the kaiser, may he die painfully: His troops usually get the first shots in on their opponents, but a small batch of mercenary horsemen is sufficient for throwing them into disarray for long enough for the pikes to come up and make a messy display of them.
PS: Coseletes and Veteran As are 2,5 times as expensive as their mid-tier counterparts, but hardly 2,5 times as effective. Personally, I feel "moar guns!" is more efficient than "Marginally better gunners!". Especially since it only takes one shot to kill one of them.