Jedi or sith in arena

Honestly I'd stick with jedi for now. Get that zeta on Bastila lead and run circles around those Palp teams. If you're just getting to that point where people are barely getting zetas, they certainly aren't going to be anywhere close to getting Darth Traya, and a Zeta Bastila team will destroy a zeta palp team on offense and defense granted that the enemy doesn't have Traya. zBastila, GMY, Old Ben, Nest, Talzin is a great team to stomp over Palp teams. You might want to reconsider Talzin at some point and replace her with Ezra for more synergy, and eventually getting Hoda in place of Nest. Old ben almost works better than GK does in some cases so he should do you good for a while.

If you start going Empire now you're going to be behind those other teams, and your current team will out-perform them once you get the zeta on Bastila's lead.