The whole human mind is free but peace of mind is priceless!
I personally don't see the point in paying for data storage. I have 2 iPhones and 4 iPads all on my account and never needed any more storage then the 5gb they give you free. All my photos and important documents are stored free on different sites. IMHO if your paying to store data it's like throwing money away. what exactly are you lot storing in iCloud?
I don't recommend any one use shoebox, they resell your photos.. Read the t&c first, Dropbox is probably second best can get nearly 23gb free.. But nothing will beat apples iCloud, is does so much others can't..
If only they had an android app, I would move from Dropbox.
If you change from the older iCloud Photo Sharing to the newer iCloud Photo Library them all photos get uploaded automatically. Also (as an option) once the full-resolution copy is safely on the Cloud the copy on the device can be downsized to a thumbnail copy to save space. If you actively look at the thumbnail it reloads the full- resolution version.