So I just received this game after purchasing several games during winter sales and I'm loving it so far. But unlike other General series where I can determine easily which unit is good against which unit this game on the other hand can be a bit vague. When I played this game I'm surprised that the peasant unit is actually pretty competent and the dragon unit is kinda weak. Are there good tips for me (and the rest of the newbies) to play this game?
Terrain's quite important, and manoueverability as well.
Heavy infantry are the strongest units in game, in terms of raw strength, but light infantry get a relative advantage in rough terrain and attacking into (from?) rivers. And skirmishers will damage both types of infantry without being attacked back, which can be used to whittle down stronger units. Light infantry and skirmishers are really cheap too, and you can use that to offset other parts of your army that might be very costly e.g. sky hunters.
Units which skirmish (skirmishers and light cavalry) only take half damage if they're defending against melee units. This makes skirmishers good against almost every type of unit other than cavalry - which are faster and will do full damage.
(Heavy) cavalry are strong enough to pack a punch, and great if you can charge them into archers, skirmishers, siege, or casters. They're not going to do that much against light cavalry though, bad against light infantry in rough terrain, and a lot of heavy infantry will defeat them in open ground as they negate cavalry 'charge' bonus. Good unit to have though.
I like light cavalry, they're fast and survive well against most enemy units, but they don't do a lot of damage against stronger units, and are expensivish. They have search range bonus which is great for spotting the enemy forces early on a map (and I usually give them items to enhance search further).
Sky hunters (wyvern>dragons) are weak, but important, because they are so manoeuverable. You want to protect them and I like giving them magic items to help. Against siege and bombardiers, they're very strong, and they also are great for finishing off weakened enemy units. They are considered essential to have - you don't want the enemy to dominate the air.
Bombardiers and siege are useful if you want to break down strong and entrenched heavy infantry in fortifications. Siege let you hit a unit multple times, but are really slow and vulnerable, lots of players recommend not using them. Bombardiers are safer and faster but you can only bomb from the hex directly above (not usually an issue except for REALLY entrenched and heavy units).
Casters are slow, weak, and the abilities might be situationally good. I don't use them much.
Don't specialise too much in one or two types of heavily upgraded unit - the game knows to detect that, and it punishes you by throwing heavily upgraded units. I don't know what the formula is really... at the most I usually have a quarter of my army being one type, and I've never noticed this problem myself.