Dwarves are best with Guns and Artillery. Their infantry is designed to hold the line - Basic ones with shields are enough until you get to Ironbreakers. Ironbreakers are the best defensive infantry in the game.
Focus on ranged first, Quarrels are good early but as enemy gets armour switch to guns. Flamethrowers are also good but finnicky to use if Orcs and Skaven go monsters. But against infantry they melt
Grudgethrowers are amazing, have like 3-4 in your early armies and they will shred the enemy infantry to the point they get in crossbow range they will be weak.
Mid game get Organ guns, they are the best. Flame cannons are good if you know how to use them
Early game - 5 infantry to hold the line, 2 Runesmiths if you can. 4. Grudge throwers, That's 10 units so far, 1 lord so 11, engineer if you are lucky, if not fill the rest with quarrels
late game - 5 Ironbreakers , 3 organ guns, 2 flame cannons, 1 lord ,1 engineer, 1 rune smith rest thunderers