I guess my answer would be "it depends".
What are your plans for diving? Blue water Carribean, lake, river, cave, etc? Shallow diving or deep, or both?
I would suggest going and talking to a couple of your local dive shops. They'll let you try stuff on, and can give you some pointers on gear purchases. Most ones I know will let you "demo" the stuff from their rental gear, and fully apply the cost of the rental to a purchase.
ANY gear you buy you'll need service for it. It does you little good to get a "deal" on some gear, then find out you can't get it serviced.
On the BC's, there are different styles (vest vs. plate). The type/style will also depend on whether or not you're in a thick exposure suit, or in trunks/skin. Your orientation in the water depends on how overall buoyant you are with what you have on at the time. For instance, people that try on a wing/backplate can get freaked out on the surface, as the floation is on the back, which means it's at the surface, with a tendency to put your face in the water. Again, depends on weights at the moment.
Your air-delivery system and alternate are keys. I would say get the regulator thats breathes the easiest for YOU. Get the same reg and take it down on a deep dive. Does is still breath smoothly? Ditto for your alternate. Your first stage should definitely be environmentally sealed, which means water and silt is kept out of it. If you're doing cold water diving, get a cold water mouthpiece (keeps your lips warm). You have to research piston vs. diaphragm regs, too (again, ask a dive shop!!).
On your guages/information system, I'd say go with a computer right off the bat. But if you're ever going to do Nitrox (which I recommend over the long haul), make sure the computer is Nitrox compatible, at least up to EAN40 (your dive shop can explain all of this). Your regulator setup also needs to be able to handle Nitrox, too.
Above all, gather information before you buy. Most dive shops will give you a package deal. Many will zero interest finance, too. If you think you're going to save a ton of money by buying stuff online, read the posts on the warranty nightmares some folks have had. Also ask yourself what you're going to do, when you find yourself packing for a trip, and you find out, two days before the trip, that some piece of gear you're packing isn't working. If it's your local shop, and you bought the stuff there, they'll bend over backwards to loan you one or get yours fixed. Mail order on that? Forgettaboutit.
I made the mistake of going "cheaper" when I bought my family's gear. I've spent the last three years buying new stuff. Had I bought good stuff from my local LDS first, I'd be about 40% ahead of the money I've spent over the long haul, on service, mail order crap that shows up defective, etc.
Just my two cents (and no, I don't sell gear).