Shards for consular and Chewie readily available as rewards during game play so promoting them will be easier. The rest are a little more scarce, but available. Will have to rely on gear and level until you can promote the others. I'd focus on consular since he heals.
Dooku and Talia are readily available so easier to promote. Talia heals and Dooku is deadly at 4* with 100% counter so definitely focus on those two. Maul and Bane should be okay at 4 & 3 for a while with gear and leveling. The dark guard has some shards floating around so available. I hear I-86 is good but he and the rest will be a little more work to promote because I don't recall there being many rewards for them.