Need veteran opinions

Amanda • My name is Amanda. I am a fourth grade teacher and pregnant with my first baby. Mary Scott is due in May! 💕
First time Mom here and wanting some input. When do most people start registering for items on their baby registry? 
Also, what are some things that are not worth registering for? There are many things I thought about getting, and heard from veteran moms they never used it or wished they had gotten something different. This is all very new, exciting, and overwhelming 😊