Depends entirely on the person and what they like.

This is no different than asking someone for top three tv shows for someone new to TV.

But that being said.

Mushishi anilist.co/anime/457/MUSHISHI/

Supernatural, mystery vibe.

HUNTER×HUNTER (2011) anilist.co/anime/11061/HUNTERHUNTER-2011/

Cult classic, superpowers & adventure.

Yuru Yuri anilist.co/anime/10495/Yuru-Yuri/

Slice of life, school-life, cute