Is there a simplest way to make ringtones on Apple Music?

You can make a custom ringtone in GarageBand for iOS and export it as a ringtone. If you want a song, go to the ringtone settings on iPhone and click on "Tone Store". There, you can buy ringtones for very low prices through iTunes. Note: These are separate to songs - you can't set a song purchased through iTunes as your ringtone. Unfortunately, there aren't many songs on this store.