You should call B&H(or Ado or Unique or Calumet) and talk to a human. B&H especially, as the size you need of a given product may not be in the store on a given day.
Give them a day or two warning, and they can help with the alphabet soup of versions in case they don't have every version in every size. They also have other customers doing small amounts of processing. It is much cheaper buying separate chemicals. With c41, ra4, and e6 you can use common concentates if not working baths for fix, bleach and more once you are more familiar.
For now don't sweat it, just ask people who are selling to lots of small users, and have fun, not stress.