How/Where to level up ?

I'm level 20 ish and getting to the point of Bethesda Susa. There is some Jotun there throwing highly effective axes my way and through a mix of temporal manipulation and a warp hole (roleplay mode helped on my first try).

I figured I need to fight and explore more but I'm stuck between fights too easy to make any exp and going too far out to barely survive.

Any tips for areas to go to, maybe by level bracket