I'd suggest BCD (or back-plate / wing) - you can chew on any regulator available, but you need a boyancy compensator that fits you. BCD / bp-w will also have a large influence on your diving, ideally you'll begin grow more aware of good in-water position (horizontal). Regulator won't influence your diving style, bcd/bp-w is also less technical then a regulator.
Not a regulator - when renting it, two people have checked it out (LDS and yourself). If you don't trust the dive shop to give you a functional reg, DON'T DIVE WITH THEM. You'll have the rest of your life to be independant, let someone look over your shoulder for a few more months. When you buy a reg there is no supervision.
Best,
L
I concur.
If you're worried about germs (seek help) on rental regs, just dip the mouthpiece in some Listerine for crying out loud.
As a new diver (and throughout your diving life, for that matter), the single most important thing to work on is your BUOYANCY. Since you already have your wetsuit, the single most applicable piece of gear is your BC. All regs work the same way: Insert reg, breathe. There's nothing new to learn there. But renting a different BC every trip is a great way to guarantee confusion as you learn it's in's and out's, where to reach for the inflator, what type of buttons on it, etc., every time you're handed a different model.
Scuba Diving: It's all about buoyancy.
Only after the BC should you go for regs, and only after regs should you go for a computer. Tables work just fine and don't cost a penny, and frankly at this point in your diving you should be staying shallow, and your air supply will determine how long you can stay down more than the no-deco time limits.