I'd go for:
1x Imperial Aces
1x Millenium Falcon
And B-Wings when they appear
And maybe later (as it's a bit hard to use well when first playing)
1x Lambda Shuttle
and maybe second Firespray / Falcon
And Rebel Aces when it appears
I don't think you need any more of the following for now.
^^ this. Nothing to add, really, except... How can you live without the Millennium Falcon?
(Also, some really good upgrades come with the Firespray and Falcon)