Arena Squad (Overall roster advice) - HELP (Level 73 F2P)

@godgiven45 is right.
Try this: Dooku (L), Phasma, RG, Kylo, GS
Star/Gear/Ability up all of them as much as you can. RG is good even at 4* if you have him geared up. You can sub out Kylo with Lumi if lots of dooku(L) around.

GW may get little hard but you will be able to make it. As more and more of your toons reach the max level GW will start getting easier. Anyway you have a great GW squad. Lumi, Daka, Ventress, GS, JC should pretty much get you right till node 10 easily.