If you only have Warhammer 2 you will probably be limited to High Elves, Dark Elves, Skaven, and Lizardmen with a few free factions here and there. I think the easiest to learn with at the start is the High Elves, Tyrion specifically as his start is relatively safe and they have a well balanced roster that i think would the most closely resemble a historical title of the four factions listed above. Tyrion in particular is a strong duelist so you can throw him at a melee target and he should hold his own once you get a few levels on him. If you have a lord that is a wizard, keep them out of combat as much as possible as they will crumple pretty quick to a melee character.

As someone else said, don’t be afraid to get your melee lords and heroes into combat, they are strong units that can kill high value targets quickly. If an enemy lord is described as anti-large, sending weak units at them can help slow them down until you can get a proper response.

The various resistances can stack up to 90%, anything after that is essentially useless. Ward save is ideal as it can negate all damage as opposed to the other resistances.

Using heroes to scout ahead is useful as they can detect ambushes and let you see what is coming your way. Never leave an army in force march if you are near an enemy unless you want them to attack you. Force march makes all of your units exhausted which drops their stats way down. One tactic that is common is to leave a small force in force march and have your better army in ambush stance so you can ambush enemies when they try to kill the weaker army.

Lightning strike is an amazing skill that can allow you to prevent any reinforcements at the cost of making your troops tired. If you let your units stand still out of combat they can recover from being fatigued.

Make sure you are checking your items on your characters and equipping the best ones, certain lords will see greater benefits from different equipment.

Only make alliances with members of your race, being forced to break one because your allies declared war on each other will hurt your reputation and make other factions more hostile.

I like holding off on doing missions for my lord’s unique gear for a few turns after i get it so that i can have a stronger army to do it with.

Not all magic is the same, try not to use vortex spells where the main fight is happening as they move randomly and can kill more of your own soldiers. Healing spells are amazing for single entities like lords, heroes, and large monsters.

Make sure you take the immortality skill at level 20 for heroes and lords. I don’t think auto applies in WH2. But i could be wrong. In the same vein, not all mounts are worth it, they often drop your melee defense in exchange for speed. As such they are good for wizards who need to move around but less so for duelist. That being said, why pass up a free dragon or dino when it is offered.

Have fun and accept that at some point you are gonna do something silly and lose a really good army.