Went with the Gaim, as they were the most active political power in the series from the list, even if we didn't see their ships in action. Even remember an episode where Sheri' is trying to get the Gaim to protect the Brakiri from the Shadows, so they must have a respectable fleet.
Definitely don't want to see more EA, there's way toooooooooooo many earthers out there already. For a young race they are already way to powerful too.
Also don't want to see the thirdspace things, haven't seen the movie but have herd it's frelling awful, and if they could easily crush the shadows/vorlons, who'd they be fighting, a grand alliance of the other first ones every battle?