i had a buzz cut 7 months ago and now my hair is shoulder length. this is what i do:

-pantene ‘repair and protect’ shampoo and conditioner in the shower - pantene ‘miracle rescue’ hair mask in the shower. while this is in my hair i use a scalp massager (i shower and wash my hair every day because i work in the service industry) - pantene ‘miracle rescue’ 10-in-1 leave-in conditioner - chi ‘silk infusion’ leave-in - i brush my hair with a wet brush when it’s wet - i use a bristle brush when it is dry to stimulate my scalp (i brush it like 3 times a day with this)

other than that, try to not use heat on it. if u do, use the coolest setting. i don’t use a typical hair straighter, i use a straightening brush that is ceramic and infused with oils. (i think the best thing u can do is keep it in braids once it’s long enough, to avoid breakage or damage) i also try to avoid hair cuts for as long as possible, until i literally need to get it shaped/ trimmed.

i hope this helps! good luck