What other people said + forget being ready for Palp and Thrawn. In those 6 days you will probably manage 4*. As a tip - you need to exclusively focus on them, no other farming, do energy refreshes as much as you can afford.
Mods:
Run Mod battle 1-B until you have 1-2 dot Speed Primary arrows for all 5 of them, after that finish Mod Battle 3 so you can do Health Mod Challenges. There you need to make it to Tier 3, after that sink all your energy in Mod Challenge Tier 3 until you have decent mods for your guys. You can see the suggested mods here:
http://apps.crouchingrancor.com/Mods/Advisor
Waste no energy on anything else except Phoenix. At level 54 I feel you are very very late for the party. I started with Phoenix straight away and got into a new Arena shard. The results at level 59:
19 out of 19 Galactic Wars finished
Consistent top 20/top 10 Arena Rank
Zeb, Chopper and Kanan at 6*, Ezra 10 shards away from 6*, Hera 5*
Gear level 7 1/6 and 2/6 across the board.
All skills maxed (level 5 on most, level 6 on primary).