Assuming you haven’t played it, Dark Souls 1 is a pretty good introduction. Great level design. (Best in the series imo) Easy learning curve, and still holds up as a solid game. Mechanics might be considered a bit clunky by today’s standards.

People love Bloodborne but its a lot more fast paced than the Souls series and not what I would recommend as in introductory game.

Nioh is also a decent game for introduction.

Have not played it myself but have a friend who vouches for Code Vein