How do some players have insane amounts of stamina?

Newer player here! I’ve seen some posts with people with actually insane levels of stamina or gold saved etc. I’m talking like maybe 200 stamina limit but 3000 stamina available??? How do you get it so high? Is this just long term players or are you spending real money to get to this point?

What is the best way for me to level up? Do I have to spend real money?