For beginners, some highly recommended K-dramas are:
Crash Landing on You:
A romance between a South Korean heiress and a North Korean soldier.
Goblin (Guardian: The Lonely and Great God):
A fantasy romance involving an immortal goblin and a high school girl who can see ghosts.
Descendants of the Sun:
A love story between a special forces captain and a doctor set against the backdrop of a peacekeeping mission.
Itaewon Class:
A story of an ex-convict who opens a bar in Itaewon and seeks revenge against a powerful conglomerate.
My Love from the Star:
A romantic comedy about an alien who has been living on Earth for centuries and falls in love with a famous actress.