I disagree with J about the price... you don't necessarily get what you pay for, and some of the worst available gear is quite costly. Other high priced gear is very good, but makes use of unnecessary and expensive materials like titanium. Better than buying the most expensive kit for it's own sake, research (outside of asking dive shop employees who are motivated sellers) what brands have the best reputations for quality and performance, and go with those.
I think you'll get plenty of agreement with regard to the regulator and BC, but you'll also want to select some sort of pressure, depth, time, and direction instruments.
With the BC, I'd recommend renting both traditional and back-inflate systems several times each until you decide which style you prefer, and then trying to select the simplest and most durable BC of that style that has the features you want. Personally, I like stainless steel hardware, dislike velcro, am somewhat picky about where my D-rings are placed, and don't want any strap across my chest that might interfere with a dry suit inflator. Other people like zippered pockets, ditchable weight holders, and a variety of other stuff. Get what works for you, but avoid the H.U.B. systems made by several manufacturers.
For regulators, I personally use Apeks regs because I like their reliability and the way the hoses route, but Scubapro is also a popular and very highly regarded brand.
As for instruments, I find the big all-in-one consoles to be unwieldy and conducive to poor streamlining, so I don't use them. I have a small brass pressure gauge that I keep clipped off to my BC so it doesn't smack into things or get tangled up, and wrist mounts for my Uwatec bottom timer and my Suunto SK-7 compass. I like the wrist mounts because they keep all of the information where I can see it easily, because they're streamlined that way, and because I don't need a free hand to check them, which makes ascents easier. There are lots of bottom timers, dive computers, and analog gauges available... again, use what makes sense for you.