let me try and help you with your problem.
i am a vet from hundreds of games, all the way from Shogun TW to MTW2 Kingdoms (ETW too much for my poor 3 yrs old laptop), and ive found one absolute truth in all warfare: production wins wars.
allow me to explain:
the more money you have, the more equipment you can give to soldiers
the more equipment you can give to soldiers, the better.
simple.
in order to win as any faction in any TW game (or any war game, i guess), is to start making as much money as possible. without money you cant fund war, you see. anything else other than income is a second priority.
so, how do you make money? to answer that question, ask yourself: where do you spend money?
lets try to number the reasons:
upkeep, building units/buildings.
but of course, building the right kinds of buildings net you more money, ergo more income. so, your first priority is to build money producing buildings.
without going into much detail, buildings that produce money are farming upgrades and trading buildings (markets and ports apply). build these whenever possible.
tax is most important. as a rule, big cities should be taxed until city happiness reaches 75 to 80%. any less and cities will revolt. smaller cities have less citizens to tax, and higher taxation drives population away, so keep those to low tax rate.
finally, returning to a point established earlier inpost, lets talk about upkeep.
upkeep is what you pay someone so he can do a task for you.
soldiers require upkeep.
solution? disband soldier.
if you see a small village guarded by the equivalent of an army of swan knights of dol amroth, then you may be mentally unstable your strategy must be well planned and dont need to read this post anymore.
the trick is to keep the very bare minimum number of men guarding any given place of importance (read: village). anyone else who is not a necessary warrior may be disbanded at will.
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execute all these tricks at the very first turn of the game. money should now fall from the sky. if problems persist, consult your nearest Maiar or call 555-4263253 if located near Minas tirith, (02) 133-728766 if located in near premises of Barad-Dur, and 123*7278626 for Rohan(*)
*Fangorn Forest not implemented into service.
if you didnt get the phone reference, open spoiler (if you got it, w/e. open it anyway, like you would listen to warning):