My wife and I are starting our journey of building a hobby together. She has had fresh water tanks in the past and has a planted fresh water tank in her office at work. We have decided to start a salt water tank at home so we can both learn from ground zero together and build an indoor shared hobby to give us something unique to focus on during the hot months of summer in AZ. We've been reading, watching videos, and visiting local shops here in AZ. Our goal has been to install our first tank in October and kick back and let it cycle while we formed a vision for our next steps. The more we learn, however, the more it seems we need to think through, buy, and set up before we even buy a tank & stand. Perhaps joining Reef2Reef will help us narrow down which things are vital and which things are seen as important by those who have been in the hobby a while, but don't need to bog down a newbie.
Welcome to the saltwater side, and what a great way to spend those brutal AZ summers together. Joining Reef2Reef is a smart move. The community here is generous with advice and will absolutely help you sort must haves from nice to haves.
Since you asked what to prioritize before the tank itself, here is the short version most experienced folks would agree on.
RODI water is non negotiable. Tap water in most of Arizona is loaded with minerals and contaminants that will cause algae problems and stress livestock. A basic RODI unit is one of the first purchases that actually matters.
Quality salt mix, a reliable refractometer, and a heater rated appropriately for your tank size round out the true essentials. Do not trust the cheap hydrometers, they are notoriously inaccurate.
Return pump and a decent skimmer if you are going the sump route are worth researching now, since retrofitting later is more expensive and disruptive than planning ahead.
Lighting can wait a bit longer since you will not be adding coral for months, but it is worth researching early since good fixtures are an investment you want to get right the first time.
Test kits for ammonia, nitrite, nitrate, and eventually alkalinity, calcium, and magnesium will become part of your routine once cycling begins.
Everything else, the fun stuff like rock aquascaping tools, protein skimmer upgrades, or automation gadgets can absolutely wait. Do not let anyone overwhelm you into buying everything at once. October for cycling is a solid timeline, that patience will pay off. Welcome aboard, and enjoy building this together.