Newbie - need help

Thanks for the advice. Quick update. I'm now level 65 and have
5* AA, gear 7 (9 shards away from 6*)
6* Lando, gear 7
7* Biggs, gear 7
5* STH , gear 8 (54 shards away from 6*)
5* Luke, gear 6 (can upgrade right away to gear 7 if needed to. Only considering mk 8 blastech weapon mod for Biggs)

Based on what I read before, I should be able to obtain a tier 5 Emp. Palp. now more comfortably.
What about a tier 6? What do I need to win tier 6?

I also am working on Chirrut. I have him currently 4*, gear 7. Noticed it's quite a slower and more expensive farm (using crystals primarily) and also needs lots of ability mats.

Other chars that I currently have worked on.
Boba Fett, 7*, gear 8
Rex, 5*, gear 7
Darth Nihilus, 4*, gear 6. Not as great yet as I had hoped.

Guys, I just wanted to update you that I cleared tier 6 of the Emp. demise event!
However not without paying a big price for it (:
I had to try for at least 30-40 times and get Luke up to gear 8 and level 72. I also had to use almost 24 purple ability mats to upgrade several toons like AA , ST Han and Luke. In addition I spent almost 1.5m in credits to also upgrade mods or level characters up to lvl 72.
Hopefully it was all worth it:) However I decided to set my focus for now on Wedge to complete a good rebel team. Then I have to choose between Baze, Chirrut, Ep Palp or work on my scoundrel team.
Thanks all for your advice and help! It was greatly appreciated!

I do have Boba Fett already at 7*, gear 8 and have a 4* DN, gear 7. At one point I will continue to farm Jedi Cons. and Lumi as well, but I think there are other higher priorities for me now with the aforementioned characters. I also think once I have Chirrut really geared up that he maybe able to substitute for any healing characters together with Wedge and AA in galactic wars.

Yeh, the only problem is that I really only have DN and just have EP and Vader unlocked. Plus I have a shortage of purple ability skills and the drop rate right now for me is close to zero. I'm closer to a Jedi led team right now with JC, Asoka, Lumi, Mace.

Okay, I'm level 77 now and have the following roster https://swgoh.gg/u/teamrex/collection/.
In the meantime I got Wedge and Palpatine but still have a hard time getting into the top 100 and staying there.
I need some advice again.

I have the opportunity to promote Rex to gear 9 and St. Han as well. If I wait though, I may be able to use those gear pieces though for Chirrut or Boba.

What should I do at this point to improve my arena ranking? It's been hard for me to get some good mods too.

I also managed to get both Chirrut and Baze which have served me well :)