Spend time talking to people, your instructor or Local Dive Shop (LDS) (or Larry at Scubatoys). I didn't decide to buy things until after my 4th pool session, when I was sure this really was going to be enjoyable to me, something I was comfortable I wanted to pursue long term (I had dreamed of doing scuba for years, just didn't have things pull together properly until recently).
Some people will say to hold off on the purchases, do rentals for a while after you get certified. It really is an individual matter. In my case I was glad to have my own reg/bcd for the final OW pool work and my certs, it gave me time to work with it with an instructor who taught me various "real world" things, practical tips. Similar with drysuits, though possibly (hopefully
you won't need a drysuit course immediately where you live, can do wetsuit diving for a season. I wanted to complete my certs quickly, so needed to do a drysuit course; I tried a shop trilam, marvelous thing, then a crushed neoprene, which I really liked.
I ended up with buying what I suspect most folks would call "midrange" on everything, not intro low-price things, but also definitely not top of the line (and $) on anything.
Some gear beats me how anyone can buy over the 'Net, stuff like drysuits, though I know that people do, successfully.
Concerning drysuits specifically, you actually wear insulating clothes under the exterior suit. You can buy custom dive-specific things, or use normal polartec (and other material) outdoor clothing. The layer of air, drysuit to your body, helps mitigate heat loss, and there are variances due to different suit material and individual heat production (I run hot, "sweat like a pig"
For discussions on individual items (BCDs, regs, tanks,...) a really good starting point is the equipment forums here.
Good luck -- it's a ball