Who to farm from Arena/Galactic War stores?

Savage and Teebo

Savage because he's the only one worth something atm from the selection you gave us. K2SO from galactic war for the cassian ship.

Heard of Platoons? Farm them all

To elaborate:

Savage because he's a solid sith and that faction is getting a lot of love lately. He's also probably the only one of those Arena characters you might actually find a use for.

Teebo because he's great to use in the Rancor. Cad Bane might be the guy to farm after Teebo just because he's a BH and scoundrel. I imagine you probably have the scoundrels you need for the credit heist, but Bounty Hunters have a TB battle dedicated to them and they might be getting a rework (speculation). Honestly, you might just want to work on ships in this store once you finish Teebo (or before depending on your situation).

Teebo and Savage.

Teebo and Savage it is. They're both at 6* already, so that'll be a quick farm. K2SO after that.

From arena shop Nute and Savage both have their uses (the nute lead zombie+acolyte team is great for TW).

From GW shop, Cad Bane and K2S0 are both usable in territory battles.

Another vote for Teebo and K2S0 from GW store. Teebo for pit and tank raids, K2 for ship and Rogue 1 TB missions.

Savage and K2.

Teebo is irrelevant and should retire.
What you need him for in the rancor raid, bistan is far better at lower gear.
On an ewok squad, he’s on the out. Pap and Log are in.
He has had his day and it was glorious but now...irrelevant.

Edit: K2 is a big part of the rogue one team (for TB).

To clarify, I own all of the characters already and they're all between 4 and 6 stars. I'm just wondering who to go after to get to 7*.