Hi guitarwizard.
If it were me, the characters I'd develop on your team, in order of priority, would be... Sentinel Harpy, Sentinel Soulless Demon, Rocket Dog, Hellhound, and Warrior Axis Bomber Boy. Your Sentinel Corrupt Droid and Warrior Newborn of Light are potential superstars too, especially in the Arena... but I'm not sure I'd focus too much on that at the moment. Sentinel Harpy hits very hard, and is a bargain to max, skill shard-wise... a fine investment, for sure.
All this having been said, from a campaign perspective, your Eddie is the most important toon on your team, so he'd be my primary focus. Either Speed of Light Eddie or Soldier would be excellent toons to focus on at this point, if you have them (I imagine, if you don't have Soldier yet, he can't be that far off?
) Hope that helps.