What should I do to improve

Stop leveling your entire roster. Pick a squad, get them where you want them, move on to the next.

There are a thousand guides out there and they all recommend starting with Phoenix and Scoundrels.

For one thing you can use a full Phoenix team instead of using Talia and Chewie.

I'm not sure what you mean by "rank 13" though.

Yes swap out Chewy and Talia for the other two members of the phoenix team you do have and STOP leveling or putting resources into CUP, Clone Sargent, the two Bugs you have and IG86

"Liath;c-1877615" wrote:
For one thing you can use a full Phoenix team instead of using Talia and Chewie.

I'm not sure what you mean by "rank 13" though.

Arena tier 13 perhaps? The team the OP is currently using is unlikely to break the top 1000 which is the next lowest tier #12. Tier 13 is the 1001-2500 prizes.