It all sums up in a few facts.
1- Class prices are very competitive and have long been loss-leaders to get new divers in the door buying gear. Gear sales is what keeps most shops in business, so of course they want you to purchase at least some of your gear from them.
2- Divers who own their gear do dive more often. Like buying and owning your own car, it is an investment. You are more comfortable and know what you are getting into everytime, rather than the surprises of rental cars trying to figure out where everything (wipers, setting mirrors, seats, etc.) is. Sometimes rentals are a necessity when traveling.
3- There are lots of brands and styles, renting BCDs and even wetsuits is a great way to test drive before you buy.
I think the one item that can make/break a fun experience is an ill fitting poor quality mask.
I require all my students to own a good, well fitted mask...sorry to say many times they show up with that pink mask they had to have and it doesn't work for them, so off we march to try on masks after we've wasted a pool session being uncomfortable. A good shop will let you exchange that mask after the first pool session for one that might work better.
Frankly a good mask, simple snorkel with purge valve, stiff open-heeled paddle fins, plus any booties, just don't cost that much ($150 +/- $50). Avoid those expensive snorkels with big gadgets on top. Avoid those expensive split fins...the fin will collapse when kicking hard in a current making you work even harder.
Exposure protection depends on where you will do most of your diving and how sensitive you are to being cold. So many many options, take your time to investigate what will work best for you. Usually stock rentals are available, but may not fit as well as they should to keep you warm...not to mention they've been pre-peed. :shocked2: :yuck:
But traveling to a climate you don't normally frequent is a great reason to rent the appropriate exposure protection for those water.
After getting your personal gear, invest in a wrist dive computer and get to know it well (many good options reasonably priced)...and it travels well
. And don't forget safety items like DSMB (the bigger the better), whistle, finger spool, etc and always take them with you. It sucks to need it and you left it at home/in your hotel room, etc. Think of them as the spare tire in your car which you hope to never need but glad its there if you do.
Regulators, a good mid-to-high end quality, will breath easier, grow with you as you gain experience and will last you a good 10-15+ years when maintained well. Remember this is your life-support.
BCDs...this is the item that is replaced most often...love or like it, then hate it after a few dives - "it doesn't fit in the water when I'm horizontal like it did in the store when I was standing" & features you thought you needed/liked you don't and visa versa. Here on SB your will find many advocates for backplate & wing/harness systems for its interchangeable modules/customization and simplicity.
You've gotten a ton of great advise in this thread and there are many other great threads here full of valuable information.
Go enjoy your class and keep us posted on your progress.