I'm very new to the skirmish game (only played 3 games total), and I came up with this list as a "jack-of-all-trades". I only have 1 Core and some of the expansions.
(15) RGC
(8) Royal Guard
(6) Stormtrooper
(5) Elite Probe Droid
(6) Officer x3
For objective based missions, my thought would be to use the stormtroopers to act as shields/block the opponent from getting to the objectives while using the officers to "order" the RGs and RGC into position to take the objectives.
I think the Elite Probe Droid is under-rated and a great value for 5 points.
Any thoughts on whether you think this would be a competitive list?