The Spider exercise is useful and this mod by Justin I found beneficial, https://www.justinguitar.com/guitar-lessons/finger-stretching-exercise-te-101 . Start where its comfortable on the fretboard and, as you get better, move towards the first frets for a good stretch/workout.
IMO, it's good to start a practice session with a warm-up and this is one of the good ones.
Good luck, have fun.
"It takes a lot of devotion and work, or maybe I should say play, because if you love it, that's what it amounts to. I haven't found any shortcuts, and I've been looking for a long time."
-- Chet Atkins
-- Chet Atkins
