iCloud storage always full
Go to Settings > General > Storage &amp; iCloud Usage. Under the iCloud section, tap Manage Storage. This will show you everything that is using space in your iCloud account. If you see something you do not want backing up to iCloud, then disable and delete it here. iCloud Photo Library may be the culprit.

On the bottom of this page you can also select Change Storage Plan to purchase additional storage; in the US, the $0.99/month plan gives you 50 GB, which should be plenty for you.