I hate to be a pain in the ass, but arms, you really need to do great form for one set, and then super heavy the next set.
Arms are my best body part. Only do arms on arm day.
I normally do
Preacher curls to failure
Dumbbell curls on a machine to failure
Curls with cables
Skull crushers to failure
Pushdowns to failure
Triceps kick back
Reverse curls to failure.
Foram curls to failure on my knees and using the bench