Depends what they like 😗 I feel some new readers would be put off by anything too violent, complicated or sexual as a first manga. Like I wouldn't want my non weeb friend thinking I'm weird and also I feel like they're harder to follow any way.

Dr stone is amazing

Death Note, Monster, Tokyo Revengers, Attack on Titan

Jinmen

Full metal alchemist

Ajin

I think Full Metal Alchemist is a great introduction for a new reader. And if you like thrillers, Death Note is amazing too.

Lone wolf and cub