iCloud Storage

What should I remove from my iCloud backups because it’s starting to take up all of my iCloud storage and I don’t really want to pay for more.

I currently have everything toggled on to be backed up but I’m just wondering is there anything that doesn’t really need to be backed up , like for example does say Facebook and messenger and other social media apps needs to really be back up ?

I don’t understand iCloud backup completely I just know it backs up like photos and contacts and stuff which that’s something I always will keep backed up I’m just basically asking do I need to have all these other apps that I have turned on could I turn them off.