As im a nab maybe this wont help so much but still.
If u fight bots (hard and very hard) you must now something (not really but) -bots make only dragoons but a ton of em and some of em make riders (turks and ukraine make a lot of cav) - bot ussually makes patrols of arround 40 men (16 archers and others are grenadiers.-Most of arty that bot makes will be mortars and u must upgrade ur pikemen alot if u want to match ur enemy.
Bot ussually put ranged units behind inf so if u send a group of light cav u can rape his ranged units.
Now on beggining- if u have hills near your base put some ranged units as watchmen (arround 15-25) and hope theyre gonna slow down the enemy army
Now if u wanna slow down the enemy army u can send arround 15 light cav (cossacks or magyar cav) and run arround so the enemy army follows you until you split em in 2 armies.
Now about economy (my economy is horrible) you must get a ton of wood and a ton of food and even more gold and coal if u want a cav army or a ranged army and a lot of iron for inf. As everyone says u must have more mills and more town halls and more and more and more and more!
You must have some kind of a backup unit (even 10 pikemen hidden behind a house can help) if u get raped and if u have a cav based faction (like poland or ukraine ,but magyar and turks are good too) recruit a lot of cav and keep em behind and send em to raid the enemy. If that fails never mind ur gonna save some food but it better works cuz u can deal a serious hit to enemys economy by making him loose 2-3 mines and a mill.
So i hope theese tips can help u to be better then me in this game.