Some things I learned.
As far as when to buy what, a lot of it is a combo of what you can afford and knowing or learning what you like and what you will need to do the diving you plan to do later. Always buy for the future, training wheels have no place in diving since its better to have top end gear on a shallow dive than cheap crap on a deep dive. All you waste is money rather than safety.
Also its good to standardize your full kit sooner rather than later since familiarity with everything in both function and location is sorta critical to not dying and all when stuff gets messed up. If you are narced and things go bad it needs to be 2nd nature to find anything on your person.
As far as brand there is no best, but there are a number of really goods and quality varies a lot from model to model even within a brand.
You tend to learn what works for you and what doesn't after the fact unfortunately, but rather than asking what to choose, ask people why they made their choices and ask yourself if their reasons are relevant to you. Then assume they are idiots or selling what they recommended (dive shop) and verify it yourself somehow.
Due to allergies and often missing my cue to equalize (if you can feel it you should have done it 5 feet ago) I need to pinch my nose and blow a bit harder on occasion and my current mask with its nose drain valve makes that harder because the drain valve is hard plastic. I will eventually replace it with a full soft nose version and keep the other as a backup.
Spare gear as a backup is nice.
I tend to overpower any sort of low effort fin (anything with a hinge like structure across the middle). Fins with solid sides all the way down are best for me.
Because of that same issue my feet often used to get cramped, I discovered that I needed hard soled boots to brace my feet (makes rocky beaches a breeze) but it also required the largest size fins because they take up a ton more foot pocket.
I use my snorkel on all surface swims since usually the eager to dive idiot at the head of the group is going too fast and wasting everyone's air by making it a race (I've given up trying to convince anyone otherwise), so a snorkel is not a useless accessory for me like it is for many other people (many don't even carry them). I have a dry snorkel because of that and it has never caused me issues or inconvenience, and its nice to have it close off by itself even in mid inhalation if i get swamped by a wave or go too deep by accident for some reason. Its also nice for genuine snorkeling at other times. YMMV.
For regs either buy a setup that you will not outgrow ever, or buy a used rental set of decent quality (and recent service) to use until you can afford a really great set, don't spend a bunch of money on something that is neither low cost nor everything you want. Get gauges with your regs even if you use a computer. I use an Aeris pressure and depth gauge (with little temp gauge in it) with a compass on the back and a seperate wrist computer. I also have the dive planner card tucked in my bcd pouch so my computer is really just a handy toy. Your regs will need to be serviced, take dealer location and pricing into account for your chosen brand.
Have a nice large light in your hand with a wrist strap for the dives you need it (my C4 seems small at 100 feet), and ALWAYS have a little mini mag light sized dive light strapped to your BCD either as a backup for main light failure or for when you suddenly want some light and didn't think you'd need to bring one (signalling someone comes to mind).
I hate vest BCD's because they squish me, my back inflate can't be felt even fully inflated. I chose a Zeagle$ (the dollar sign is silent, but deadly) because I love modular construction for later updates or alterations and it gives me all the gear stowage options I want with the vest I chose. Not 100% sold on the ripcord weight dump mine has, but its just as easy for me to unzip both pockets and pull the 2 yellow weight pouch thingies out if I had to even with my heavy gloves on. I chose to get the rear weight pouches because then dumping my main integrated weights dumps enough to get to the surface easily (and get stuck there), but retains enough weight to help slow the ascent (all your eggs in one basket is stupid). It also somewhat critically provides rear weight balance to keep me upright on the surface with my bcd fully inflated which some back inflate setups are rather bad about.
I use curly bungee things with quick buckles to keep my gauges tucked against my body where I can easily get at them to see them but don't have any dangling. I keep my octo reg on the type of holder than blocks the mouthpiece because that really helps prevent it freeflowing from sudden water currents and also a hose clip so it doesn't billow out.
I have all henderson hyperstrech stuff for wetsuit hood and gloves. Originally I had (still have) a 6.5mm farmer john 2 piece type wetsuit and found myself always fighting with it trapped air and buoyancy wise. A one piece is much easier to get the air out of though not as warm overall.
Unless you dive a ton buying tanks is a waste of money (purchase+inspections>rental costs). Plus you don't own a scuba compressor so you have to go to them every time anyways for fills.
I forget if I had any other brilliant thoughts to share, its rather late.
