Wuthering Waves offers free Resonators, which will be accessible to all players. There is at least one free Resonator in each element, from Aero to Spectro.
All Free Characters in Wuthering Waves

Rarity

Element
Multiple
Weapon

Source
Starter
How to get
The Rover can be acquired in the Prologue when playing Wuthering Waves for the first time. The first element or attribute they’ll have is Spectro.

Rarity

Element

Weapon

Source
Story
How to get
Yangyang can be obtained by progressing through the Prologue. This is a few minutes into the game.

Rarity

Element

Weapon

Source
Story
How to get
Chixia can be acquired by progressing through the story. She will join the party once you reach the first town, around 20 minutes into the game.

Rarity

Element

Weapon

Source
Convene
How to get
Baizhi can be obtained by playing through the story and doing the first Convene, roughly 35 minutes in or more.

Rarity

Element

Weapon

Source
Event
How to get
Yuanwu can be obtained in the Rumbling Hollows event. You will need to complete the Tower of Adversity’s Stable Zone challenge.

Rarity

Element

Weapon

Source
Event
How to get
Sanhua can be acquired through the “Gifts of Thawing Frost” on Day Five. You will just need to login daily and claim.