Backing up your Backlight website is a piecemeal process, but not difficult.
It is entirely unnecessary to back up your albums or album sets. Your images, their metadata, and album settings including title, description, page copy, etc. all exist within your Lightroom catalog, in your Publish Services collections, and will be included in your catalog backup.
It is also unnecessary to back up the installed Backlight application from your website. The latest versions of Backlight and its add-ons are always available to be downloaded from The Turning Gate, either via your order email or via order retrieval.
You should back up these folders from your website:
The /custom folder contains your personalizations, if any. The /data folder contains Backlight's settings, templates, etc.
If blogging on Wordpress, then back up your Wordpress database separate from Backlight.
If using Backlight's Wordpress Add-on, there is no need to back up your theme. Otherwise, do back up your Wordpress theme, or any child theme (whether based on Backlight's add-on or not).
To restore a site from Backlight, you should: