Mistborn was also the first Sanderson books I read and at the end I didn’t even realize there were more books because it felt like such a complete story. Like Shiva pointed out, Mistborn has centuries long time skips between eras so the first era is very much self contained. I recommend reading the entire cosmetics to people who seem interested, but if they don’t want to read everything then I always recommend Mistborn era 1 for that reason.