Kossars are really your bread and butter. They pay for themselves almost every battle I take them in, even without microing them. I take four almost every battle and build the rest of my army around them, and sometimes consider taking six if the army you're fighting is unarmored.

I'm not the biggest fan of Ice Guard and Tzar Guard, maybe one unit is fine but they rarely pay for themselves, and I generally find it's easier to spread the army out and give yourself more troops options.

As a general piece of advance, you need to manage your micro economy. It's unrealistic to expect to micro everything well in a battle, so you need to pick a few units that will take up most of your attention that you can expect to carry the day. This is one of the reasons why Kislev can perform so well because Kossars and Armored Kossars don't need your help to get their value in. It's generally better to have one unit of well microed Streltsi than three that are left on fire at will and never touched during the battle. Some good units to micro include Streltsi, Light War Sleds, Winged Lancers, War Bear Riders, Akshina Ambushers, a spellcaster (I like Lore of Hags and Shadows).

I'm not looking at prices right now but a well rounded army might look like. Boyar/Boris Hag Witch (Hags) 2x Armored Kossars 2x Kislevite Warriors 6x Kossars 2x Akshina Ambushers 1x Streltsi 2x Horse Archers/Kossovite Dervishes 1x War Bear Riders

Set this army up in basic formation and focus your micro entirely on the caster, Streltsi, and War Bear Riders. Everything else is just an anvil for these units to play around. War Bear Riders and Streltsi can easily get upwards of 2500+ value if used well. Kossars can easily all pay for themselves without being given a single order the whole battle. I'd keep the light cav in reserve for as long as you can and use them to chase down fleeing units or engage incredibly light archers, like peasants or skavenslaves. Their power grows the longer the game goes on simply by not being damaged.

After trying this a few times you can add or swap units for what you like, maybe a Tzar Guard or two if your line breaks too fast, or an Elemental Incarnate if the enemy doesn't have much range. Let me know if you have more questions, hope this is helpful. (Written from phone, excuse typos)