In what order do I upgrade?

[DIGI3]

The order you upgrade modules isn't particularly critical: if the module has a dependency, the dependency will also get upgraded at the same time.

Just make sure to back up, and follow the steps at http://docs.cmsmadesimple.org/upgrading/old-versions.

[Rolf]

I would start with CGExtentions and CGSimpleSmarty because they are supporting modules.
Followed by CGSmartImage, a stand alone module used in templates of other modules.
Always good to first create backup of files and database!

Also upgrade your CMS to the latest release!