Having geared/leveled/starred pilots is more important than having high star count ships. For example, my 4-star Hounds Tooth is more powerful than my 7-star TIE Silencer. The difference is the pilots gear. My Bossk is G11 (one piece from G12) and my KRU is G8 (two pieces from G9). My Bossk also has a zeta and all abilities but his unique (another zeta) maxed. KRU doesn't have any omegas, but all abilities level 7.
Obviously, my Hounds Tooth would be better at 7 stars than 4 stars, but a 4 star ship with a maxed or nearly maxed pilot is much better than a 7-star ship with pilot that isn't geared or leveled.
In summary, pick your 6 ships you want to use, plus a capital ship, and buy the shards/blueprints for those ships/pilots only, and get those pilots geared up as fast as possible. I recommend Vader, Biggs, ITF to start, with the two Phoenix ships and KRU or HoundsTooth as your reinforcements, running with Executrix. (Once your Executrix is 7 stars, you can add a fourth reinforcement.)
