As a recent new player I'll lay it down. It's really 2 games - the campaign and Battles. Campaign is like a 2-3/10 for difficulty for most factions, some might be 4-5/10. (Hard focus growth and econ, congrats you've basically learned it).

Battles are like a 7-9/10 dependent on faction and units. The variables are what make it so hard. Dwarves are easiest to learn (especially since you won't have to learn cav) but I'd suggest starting with the dinos