Black dress shirt =/= business casual.
And business casual in a seemingly dusty/dirty job seems out of place. I don't know your profession though. You may have it all figured out.
I think without context though, that list of 'necessities' seems relatively odd.
In regards to brands of pants, it depends on how much you'd like to spend. I wear suit supply chinos and trousers all the time and love them. I used to wear Bowery slim pants from Jcrew a while back and like those as well. Im not sure the fit is the same as when I wore them though. Similarly, the 484 chino has always been a thread go to.
Price point is needed for suggestions though. These pieces can be bought from places like H&M and Gap or Cucinelli and bespoke, you know?