Go buy a good saltmix. There are many. I use Instant Ocean. 24bucks for a bag that makes 50 Gallons. Are you using Reverse Osmosis & DeIonized water aka RO/DI? Its not recommended to use Tap water for makeing Saltwater. Even with the off the shelf water treatments, they still can have Phosphate and Nitrate in it. If you want good advice on your system, we need more details, Picks help too.
I have a 65g tank with built in Overflow. It drops to a 20g tank under the aquarium, commonly known as a Sump or Refugium. In my refugium, i have my heater, protein skimmer, and a compartment all the water flows through before it goes back up, The "refugium" Section has 2 inches of sand, and Chaeto(micro Algae). The Chaeto eats Nitrates and some Phosphates, the skimmer removes the rest. a Return pump pumps the water back up to my tank through 1/2" PVC pipe. My SG is 1.025, That specific Gravity. A measurement that deals with how much salt is in the water. If you do not have a Refractometer(tells ya the SG)
Refractometer for reading salinity w/ Free Calibration fluid - Bulk Reef Supply
If you dont have a refugium, or your tank doesnt have a built in Overflow, Overflow boxes are available, and DIY Overflows are easy to make.
BRS 4 Stage RO ONLY System - 75GPD - Reverse Osmosis Systems - Bulk Reverse Osmosis Filters & Systems - Bulk Reef Supply is a decent RO/DI system, making roughly 75 gallons per day if you need it. There are bigger systems, depending on how much you need.
Instant Ocean Sea Salt Mix - 160 Gallon - Bulk Reef Supply
Red Sea Aquarium Salt Mix - 175 Gallon - Bulk Reef Supply
those are 2 popular choices in Salt mix.
But, we need details about your system to give good advice...and as Dmatt88 and other will say...PICS are helpful too. Make sure whatever hardware you buy(skimmer, reactor, RO/DI) is name brand, even if its "Bulk Reef Supply" Brand. I like BRS. Whatever you get from them, they always have parts for.
and Hello/welcome to RS, Glad to have you.