Rather than answer how to select the right gear, I'll share my "new diver buying gear" experiences as an example of what I'd suggest
nobody do.
I rented/borrowed gear for my first 15-20 dives. In retrospect, I probably would've pushed that number closer to 50 before I bought much of anything beyond mask, fins, wetsuit. Nobody can really say there's a hard and fast number of dives before you should be ready to buy, but I still didn't really know a whole lot of what was out there. I figured regs were regs, fins were fins (though I'd already determined I'd never choose to dive split fins again by this point), and a BC was a BC (hey, they all leak anyway, right?). As a result, I bought in to the brand my LDS had on display. A brand who, at the time, had a fancy new feature they were marketing
hard. I had moved a few states away, so I found a dealer here on SB who cut me a killer deal on a full set of regs. I bought a wetsuit on sale from Leisure Pro. Cheap fins. A mask that didn't fit right. Cheap used Al80 that was nearly out of hydro.
All that's a long way to say
I didn't really put much *thought* into the gear I was going to purchase. I just wanted gear, so I could spend less per dive, and increase the frequency I got in the water. Ideally, I'd get that gear at the best deal possible. Fortunately, I didn't pull the trigger on a BC before I started opening my eyes to the "growth options" in diving. I started to formulate an idea of what type of diving I saw myself doing ten years from now. I did research on dive destinations, read trip reports, looked at the training paths necessary to get the most out of any given type of diving, and did a little soul searching. I had nagged my parents for years about letting me get certified to dive, ultimately breaking them down when I was 12 or 13, and got my OW with my dad. Even before I won that battle, I knew I wanted to dive wrecks (who wouldn't?!). So, now almost a decade later, I started pushing my gear toward stuff that would be functional for that type of training and environment.
Lucky for me, I had a friend drooling over my regs, so he bought them off me for exactly what I'd paid a dozen or so dives prior (like I said, I got a good deal to start). I then bought Salvo regs - well respected by the Florida cave divers, they'll certainly work for me - a year or two before Salvo ceased to exist. I offloaded those at a heavy loss and replaced them with my current setup - Dive Rite regs. As of today, I still haven't even done 100 dives, but I'm now on my third set of regulators. That's not a trend I suggest anyone follow. A little more time pondering what type of diving I wanted to grow into, combined with a little more research, and a bit more patience, and I could've saved a lot of money by borrowing/renting to try stuff, rather than buying it to try it.
Don't discount a realistic estimate of how often you'll dive, either. I
wildly overestimated how frequently I'd get to dive. Part of that is absolutely my fault, but I was also led astray by a "promising" dive buddy, who wound up being more likely to prevent me from diving than enable me to do so. Had I waited to see how often I'd
actually dive, I probably still wouldn't own any gear today. But I was excited to dive more frequently, so I bought gear to make that happen. Pro tip: that's not how it works.
Short answer; don't be in a rush to buy. Take it slow and only buy something you're certain you want to dive for many dives into the future. Sometimes you may still miss the mark and wind up replacing something sooner than later, but take it from me; it's a lot cheaper to rent than it is to buy new gear every 10-15 dives
