Cantina store after QGJ:
I asked the same to @wawrzon and bought some ship building mats. But now that we can expect more of these in the GW, I'd rather go for the Jawa Scavenger. Next to the CD mods you can use him for the Jakku omega events.
The omega event is easy but you need Jawa or night sisters (3 x 3*all together), and each omega is worth a lot in the beginning. So just unlock the Jawa scavenger. (I also unlocked Chief Nebit in arena store.)
However fleet building mats should be worth considering to keep a good rank.
GW after zeta challenge:
I want to keep my fleet arena rank, therefore I will continue to farm "my" ships until 7*.
Then probably Datcha (already 4* from bronzium here) to 5* and then Phasma for Raids.