As above- yeah starter and cadre is a good starting list for skirmish.
Arcane Synthesis collected overviews for each faction and recommended lists, and generally a functional skirmish list can be build from
Starter (4 units)
cadre (3 units plus ‘free’ champ)
Heavy warjack, or substitute a second light or vehicle (1 unit)
Whatever Hero you like best (1 free hero slot)
Some of the recommended lists followed this format exactly, certainly Empyreans and AC the starter plus cadre is perfect.
Index to the faction guides is here