If you were my student I'd start by asking what type of diving are you interested in, local, traveling to dive, cold water, warm water, etc. Then go from there.
That you are certified would hopefully indicate you have your mask, snorkel, fins, and boots. Going on this I would next recommend exposure protection. Not knowing where you are makes this a bit tough. But if you were in my neck of the woods I'd start with a well fitting 5 mil suit. This would be good for temps from say 72 on into the mid 80's if you are doing multiple dives. Single tropical dives a 1.5mil, 3 mil, or even a skin.
Next the bc. Again the conditions and your interests have big effect. If you plan to do local as well as tropical that involves air travel a compact yet versatile bc is what you'd want. There are several travel bcs from various companies but I would not consider them for local diving where you'd need any real weight. Also what features you need again are largely dependent on the dives.
Pockets- pretty much useless on most bcs. Badly placed, poorly designed access, too big or too small. Go with pockets on your suit thighs. D rings- 4 at the most for recreational diving. Any more is flash and in all honesty look stupid as they force you to pile stuff on top of each other. Weight integration- ok but if you are using more than say 10lb you should have some in a belt anyway. It is not a good idea to have all your weight in one system. SO what would I recommend that will not break the bank. 1 Zeagle Express Tech-retail $250 or so- add 20 dollars worth of d rings, metal buckle, and two cam band weight pouches from XS Scuba and you have a bc that will work for any warm water and most cooler water diving even with steel tanks for less than $300. 2 BPW system- steel plate, 30 lb lift wing, HOG harness.
THIS IS NOT A TECH BC!
It's just a bc no matter what anyone says. Comes with the drings you need and the steel plate eliminates the need for the cam band pouches. The HOG harness is not much different from that on the Zeagle except it's one piece of webbing instead of two. It is also modular and will break down and pack very small. You also do not need to spend 500-600 for one of them. New can be had on sale at various places in the 350 range HOG up to 450 or so for a DSS. There are also other manufacturers out there I only give these as an example since I am more familiar with them than the others. Tip- while an excellent product you do not need to pay for a blue H logo that is of no better quality than the others.
Regulator- Again the dives. Cold or cooler water demand in my mind an environementally sealed reg. Warm not so much but the differences in prices are so that just go with a sealed. Recommendations as to brands. Well several months ago I would have said Oceanic and still would. But lately I am going over to HOG as I like there policies and the regs. But there are any number of regs that will work. You DO NOT NEED to spend an arm and a leg on a reg. I would expect to pay no more than 500-600 for a good reg complete with octo and basic gauges ( SPG, Depth). Like this
http://www.leisurepro.com/Prod/PCKG...ductID=GNSRG&SortField=Stock&DescSort=0&Hit=0
or
http://www.leisurepro.com/Prod/PCKG...ductID=GNSRY&SortField=Stock&DescSort=0&Hit=0
If you have a good dive watch you really do not need more than that to dive with tables. If you want a comp a basic nitrox computer, which is really all you need, they can be had for under 400 bucks. Here's one:
Oceanic VEO 1.0 Air/Nitrox Wrist Dive Computer
and a few more,
Suunto "Vyper" Air/Nitrox Wrist Computer, Silver
Suunto "Gekko" Air/Nitrox Wrist Computer, White
You do not need more than any of these. The Oceanics tend to have a more aggressive algorithm and the SUUNTO's are more conservative. But in any case the comp should be backup for your brain. Hope this helps.