Start the kitsune noblewoman's questline first. With this new combat system, you go through a forest fighting goblins looking for the letter, which you can increase your level through. There will be lootable barrels and boxes as well that, due to a bug or missed bit of programming, you can loot multiple times, allowing you to get unlimited potions. When you get strong enough, you automatically kill whatever mob you run into, allowing you to farm up levels easily. You'll also get some items that boost your stats too.
On a side note, I can't do the Elf innkeeper's questline, her doorway keeps saying its locked, but with lockpicking being supposedly removed in place of Ethereal, how do I proceed? I can't use Ethereal from the skill menu because it's only visible in the "learn skills" menu. Was it explained during the tutorial and I just missed it or was this missed during the games coding overhaul?
EDIT: Okay, I did some quick testing. If you skip the tutorial, the button to trigger Ethereal is missing entirely from the bottom left corner. I recommend to everybody to do the tutorial until this particular bug is fixed.