BL I would recommend to people who have not read / read much BL before. 

Focus on: plot, interesting characters, good relationships, 'verse-building, completed novels.  

Also included: Novels that 'set the genre' - including ones with toxic tropes (looking at you, 'kiss me liar' and 's*um villain's self saving system')

Avoids (as much as possible): toxic tropes, Mary-Sue characters, cookie cutter plots, plot-holes.