Rate team pls

We don't know who else you have on your roster. A tank like royal guard, Other sith, toons who add dots e.g canderous. Palpatine is next level lead for you at a guess.

register your account on swgoh.gg and post the link to your profile so people can help you we cant guess to which toons you may have @Erebos

I would definitely not recommend RG.
You should be pursuing a long-term meta team while making the 1 you have viable. Assume Thrawn's capital ship will keep competitive, go TFP to team up with. Tarkinn is farmed in arena reward, TFP fleet arena, and magma trooper GW rewards. I would go with Tarkin for the ship while you farm Phoenix OR just farm KOTOR while building up
Vader Dooku TFP Tarkin FBS

This path gets you toward the most powerful arena meta while giving you competitive ships.