You can use dip strips to check your water balance twice a week, or if you have a local dealer bring it in for a water test. Usually at NC. Dip strips keep you close, water test will pinpoint.
You can use Bromine or Chlorine. Chlorine ‘smells’ less and easier to use. If you have a well for water supply you want to put Metal Gon or similar product in each new fill.

Once filled it needs to be balanced. You want to get the Alkalinity established first, then PH. There is only Alkalinity Down, no up. For PH there is Up and down. If Alkalinity is low you would use PH up to get it balanced and then check again. Water hardness is also important. If low(soft) you would use a Calcium booster product.
There is also a Shock you would use as well.

Water should be changed every 3 months, 6 months at most. Every 2 weeks rinse your filter(s) and once a month clean w/Cartridge Filter Cleaner. Filter life is about 12-18 months. Once a year get a product to clean plumbing out which is added 24 hours before you drain water. Important to keep water balanced for internal components.

It’s usually 220v w/a 50 amp breaker service. To figure cost breakdown you would need to get the energy guides of specific tub.(just like appliances)It’s really inexpensive to have a tub, especially compared to the spas benefit to the body/health. Pads can be poured or you can have a 6” base of fines.