As you all know that icloud comes with 5GB of free space.
Beyond that you have to pay a fee of $1/month in order to upgrade your storage limit to 50 GB.
One of the way to free space on icloud is to delete your messages in icloud which you can do easily, but usually the space occupied by messages is quiet less.
You know that most of the space on icloud is occupied by images and videos.
So, the best way is to take the back up of your images and videos on icloud to some other source may be your external hard drive, on google cloud, or some other source.
In this way you can save a lot of space on your icloud and can free your 5GB of icloud space which you can definitely use for some other purpose.