Thanks for getting in touch! This is a pretty common scenario. We have a couple of tools that can help here, one which I would recommend over the other.
Our Migrator tool allows for you to take a full or partial export of an Octopus server to import into another. We extended this feature to allow for a partial export for projects only.
It dumps all the information in JSON files which means you can script the process, but also if you don’t need all the information you can delete files or directories and they will not be included in the import.
I recommend the migrator tool as it will match on names, and also does not require all data to be imported to work.
The other tool which does a similar job is our octo.exe export|import. It however requires prerequisite information to already exist and use the same IDs across both systems. This can be preferable when you want to make sure that only DEV can make projects. It is much more rigid however.
Either tool will work, it will depend on your needs, and preferred management.
For better news we are making progress on a new feature that will make this much easier to promote releases between different Octopus instances. Very soon we will have an RFC on the blog regarding this feature which is currently named Promotions but may be changed to Zones. Either way keep an eye on the blog. It will make your life even easier when it is implemented
Please let me know if you have any questions or if I can expand on any of this information.