I think Leslie's recommendation to add chemicals in small doses and wait 30 min in between doses is not justified. When you're first getting to know your hot tub and water, I would say add half of what you think you need at first, then wait and check again, and adjust the quantity if needed before you add the remainder. Once you're accustomed to how your water responds, you can add routine chemicals like bicarbonate and dichlor all at once.
I suggest you get a Taylor test kit, 9-way, model K-1005:
https://www.taylortechnologies.com/en/product/test-kits/9-way-test-kit-for-free-chlorine-total-chlorine-bromine-ph-acid-base-demand-alk--K-1005?pageid=19Also get some Leisure Time or AquaChek test strips for routine checks.
Use the Taylor kit to balance the water after fill-up. When you've got the pH, TA, and calcium hardness levels in a state of balance and the Cl or Br levels OK per the Taylor kit, drop a test strip in and see what it reads. That will be the baseline test strip reading that you're trying to shoot for.
I make routine adjustments based on the test strips, usually adding chlorine after each use and every other day or so if not used, and adding alkalinity up every 1-2 weeks. I also use the Taylor kit about once a month to check to make sure I'm on target.