Diaper Sizes ?

I've started shopping for my baby, I'm only 14 weeks, but I figured I'd stack up on a bit of diapers and some neutral clothes (not too much for now until I find out the sex in 2 weeks🙈) but I was curious, I want to get at least 12 cases of diapers by the time the baby is here (should I get more?) but should most of the sizes be in newborn? How much big of a difference is the newborn and the size one? Which size should I get more of. Sorry to ask 101 questions lol, I'm just a bit excited and confused. Any piece of advice would help, what did you ladies do? And also which brand did you prefer and why?