I've been diving for years, but it's been a while since I've bought equipment. I bought top-shelf gear several years ago and took really good care of it so its all still as good today as when it was new. What you'll need to buy will depend on what type of diving you intend to do. I'd start with a top-shelf BC, nitrox compatible regulator, and dive computer. From there you can pick and choose. About all I dive with other than the above is a wetsuit, booties, fins, mask and a small knife.
As far as the best brands and manufactures go my info is not current enough to know. My .02 on computers is to stay away from air integrated. I have a traditional tank pressure/depth console and attach my computer to the hose. This way if my computer fails my dive isn't instantly over.
Good luck - there's nothing like diving. Go to Cozumel, Mexico. Its easy to get to and the diving is awesome.