Story mode has less content atm though it's going to get expanded this year, adventure it's where it's at.
There's really no tutorial for the combat, but you can check the "Help" section from the main menu.
Battle system isn't that hard to understand, just check what actions change your stance and build accordingly.
Here's a tip though, upgrade fade away and second wind abilities so you can get some distance with fade away and then use second wind to regain footing and get more stamina, preferably you would use spring attack -> crushing blow -> spring attack -> crushing blow and when you're starting to lose footing (text changes colour to orange), use fade away and then second wind, then just start to use spring attack and crushing blow once again, this is if you make a melee based character.
If you're going to make a mage, you should also get fade away and second wind, but this time you're using the incantation -> full incantation -> [spell you want to use] (inferno is usually one of the best, some enemies are fire resistant though so get something else too), you can regain mana by doing the golem encounter so you get "Focus energy" ability, or do the Trudy quest and get "Deep focus" ability, you can also use mana chunks that you get from the golem and due the new golem interactions, it's preferable to calm or soothe it, dominating it "breaks" it and you won't get soul crystals (which are also called magic points that you can use to upgrade spells and gear) or mana chunks when you encounter it after the first interaction.
I've never played as a ranger because of the arrow requirements, they're not that expensive but i do not like to juggle around with a depletable resource.