First time bird owner

Hey all. So i’m totally in love with birds and i’d love a cockatiel but i dont want to dive in without any preparations so i wanna ask a part of my research here. Like how big does my cage need to be, are cockatiels easy to manage and train for a first time bird owner and how to train one. I dont want to hurt or treat my bird badly and cause it to be afraid of me or not be comfortable near me. Also like what food is best and etc. I’m def gonna do lots of research online too and ask the workers in the petstores for their advice but asking here seems to be smart too imo. Thanks for the help eitherway! (I’ve had other pets before like a hamster and 2 dogs, just never an avian pet)