You will need:

• A Windows VM with guest additions (sorry, it doesn't work in Wine. XP will work though)
  
• Some sort of archive manager that supports 7z archives (either OS)
  
• The ability to download about 1GB of stuff

Here's how my XP VM was configured:

• 768MB RAM, 256MB VRAM (probably overkill)
  
• One shared folder pointing to my Linux install of Civ (well, it's my home folder that actually got shared, but you could narrow it down to ~/.local/share/Steam/SteamApps if you wanted)

When creating your mod, you may get errors saying it can't find its files. This is a problem with the SDK itself, just copy the contents of "C:\path\to\SDK\ModBuddy\Build" to "C:\Program Files\MSBuild\Firaxis\ModBuddy".

First, install Steam and the SDK as normal, then launch it. The prerequisites will take a while, as it needs to download about 320MB here. The process is not stalling. When the SDK launcher appears, click ModBuddy. It will complain that a prerequisite is missing, namely the VS2010 Isolated Shell (which is probably why it doesn't have a native Linux port). If you don't want to deal with the nightmare that is IE6 on XP, here's the download link[www.microsoft.com] so you can download it some other way. This is another 100+ MB.

Once in ModBuddy, you will need to configure your Civ 5 paths. In the Tools menu, there is an "Options" button, and at the bottom of the left pane, there is a "Civilization 5" category, containing only General. Click that. Your configuration screen should now look like this:

Here, "Civilization 5 path" is the path to your installation of Civilization 5. ModBuddy seems to be perfectly content with the Linux version of the game, which is why I said to use a shared folder. "Civilization 5 user path" refers to the directory mods would be installed. You're restricted to a subfolder of My Documents, so just make a folder in there and call it "Civ5Mods" or something. Don't try any symlink nonsense within XP, Civ 5 won't pick up the mod right away.

From there, make your mod. Kael's guide[forums.civfanatics.com], despite being out of date, is still the go-to guide for introduction to modding.

Once you get your mod built up, you're going to want to play test it. The problem is, simply dropping the mod into your game's MODS directory doesn't work. For that, you're going to need to make a .civ5mod file.

Now maybe there's a button for this in ModBuddy and I'm simply too dumb to find it. But since I can't find it, you're going to need to make the civ5mod file manually. Fortunately, this is a walk in the park: literally all you're doing is making a 7z archive and naming it with .civ5mod at the end. Using the Linux version of 7-Zip, I used the following command to make my mod file:


Then all I did was put that in my MODS directory, and Civ unpacked it and recognized it.