IMO your absolute first priority should be getting max payouts for Credit Heist. Looking at your roster, you've got the core 3 (especially Lando), so I'm guessing you can carry 2 more dead weight and succeed. But if not, that should be top of the list.
After that, agree with Phoenix as a worthwhile farm for a number of reasons, and very approachable for f2p. Skip Sabine, and work on the others. Ezra and Kanan can also cross over to be used for your Jedi squad for Yoda.
Equally with Phoenix, I would work on your ships. Whatever you need to focus on to unlock the max tier challenges (especially the ship ability materials) should be VERY high on your priority list, because that will bring you extra Omega mats, and most importantly, zeta mats.
If you've still got farming capacity left over after that, I'd pick a couple from: Leia, Empire needed to get R2, Old Ben, & Farm Boy Luke. Then start working on them. Therein lies the path to CLS, and greatness. Even if the meta changes before you get there, they are all still great characters (well, Farm Boy not so much) that you can use elsewhere or in your arena team.
