The higher rarity troops are more important than the lower rarity troops.
Now, Arena forces to pick the low rarity troops first, which locks in their colors. It is frustrating because it means often having to choose between a better high rarity troop with the wrong colors versus a poorer high rarity troop with the right colors.
This would be solved if Arena permitted selection of high rarity troops first.
best way?
Pick all troop at the same time
That’s exactly what I suggested, when arena update was released:
Congratulations! You are the one millionth customer with the exact same complaint about arena troop selection. There is no prize.
The expected wait time for resolution of this issue is: infinity plus 2 days.
Just be patient and wait until the next Arena rework in 2025 
This is it. There wont be any more Arena reworks ever.
Oh, don’t be pessimistic. Since everyone is complaining about it, their next rework will be to remove all choices and pick the team for you.
Since most troops is useful, thats totally fine…