I still use cls team (cls r2 han solo thrawn gk) all gear 12 with 3 g12 gears, fully zetaed except thrawn's unique. Yeah this team can't rule the shard anymore like in august 2017 but it still can beat pretty much any other team lineups in the shard. I've even beat a traya team (palp, thrawn, sith trio, all gear 12 except 5* Gear 11 traya, fully zetaed and omegaed)
Hardest enemies are those with very very good mod sets. Like +130 speed thrawn. But they are still beatable depending on rng. And there are only 2~3 such players in my shard so usually I can climb to 3~5th with no problem (all win) and take 1~3extra trials to take nr 1. Or 2. (Since I and another player with same payout time take turns to take 1 on rotation)
I usually spend 50 crystal for arena attempt refresh everyday
https://swgoh.gg/u/lukeamidala
(Some days when my rank is below 2nd is either: 1) I was too busy 2) I fell to 5~6th before my rank was submitted on swgoh.gg, but still after the actual payout. The .gg rank actually reveals my rank at (my payout time+7min)