I actually ended up figuring it out but thanks for the heads up. I hadn't realized there were new minors in Gauntlet's mod.

You have to update two files: factiondefs and factiontext. Faction defs needs the information in the <faction> tag and faction text will require the information starting from <string table>. You also have to upload a Foreground image, background image, logo and portrait of the race into the relevant folders of your galciv3->factions folder. From there, it's just a simple matter of updating fields to suit your needs.

The problem I ran into was I was only putting in new factions into my mod's factiondefs file, which crashed the game. When you put a factiondefs file into the mod folder, the game treats it as a replacement of the in-game mod folder, not a supplement. As such I highly recommend you copy over the major factions from the vanilla file and the pirates before you start making your own minors. Major factions can be chosen to play with or not at the main screen so it's not a big deal if they're in your file. However, when I've tried tests in which the major factions were NOT present in my mod's factiondefs, the game didn't work.

Hope this helps, let me know if you need anything more.