How can I improve my team

https://www.mut.gg/23/lineup-builder/1145a947-e598-42eb-be83-13b62ce8435b/

Everyone is 1 to 2 ovr higher because of strats, chems, and player boosts

my budget it 500k

I'd prioritize more speed for your outside CBs first. Many WRs are hitting 99 speed now either stock (Tyreek Hill) or with a theme team. Unfortunately, all of the 97+ SPD cornerbacks are pretty expensive still, but they're dropping as more and more of them are released. Someone like PS2 could be a good option for around 300k or you could spend a little more on Kaiir Elam if you depend on Cromartie's Inside Shade ability for 2 AP.

You can still get your free Team Affinity 95. Apart from that, I would indeed spend some of your coins on CB1 improvements and use your Team Captain (Allen) to improve another CB spot.