You'll definitely get many different answers to this question simply because it's all personal preference. If you're debating between a jacket style and a back-inflate style BC, if you haven't already done so, try both. There are issues with both. Jacket styles tend to be a little more unstable underwater because they like to roll sideways. But they're very stable up top because of where the air in them is stored. A back-inflate (my personal favorite) is more stable beneath the surface because the air is positioned on your back and when you're in a horizontal dive position, it's on top of you so it doesn't feel like you're constantly rolling from side to side. But on the surface they tend to pitch you forward so you have to force yourself to sort of lay back on top of it. One way to combat this is to add trim pockets to the tank strap(s)...unless you get a BC that has them included like the Zeagle Ranger/Brigade....and then add your heaviest weight to the trim pockets instead of the kidney pockets. This puts the bulk of your lead on your back which helps keep you balanced in an upright position at the surface and also puts your weight in the center part of your back, making you even more stable in the horizontal position during your dive. I personally set up my kit exactly that way and that's my experience with it.
As for regulators, you don't have to spend $600-$700 on a reg to get decent gear. I dive a Hog D3 first stage which is fairly inexpensive ($250) and it's environmentally sealed for cold water diving, too. And the hoses attach to a swivel that makes it much easier to turn your head while you're diving, too. I don't have a 2nd stage because I normally dive a FFM, but I will eventually as a backup just in case my FFM fails and I need to switch to a conventional mask. That way I don't have to end my dive and I still have an octo for emergency situations. And for an octo, the MARES Viper works great! I've done whole tank dives on my octo and didn't have any complaints. It's very low-profile and breathes great. And it's less than $100. Here's the rundown of my kit just in case you want to know.
BC - Zeagle Brigade ($500-$550)
1st Stage Reg - Hog D3 ($250)
2nd Stage Primary - Ocean Reef G. Diver Full Face Mask ($600 + accessories)
Octo - Mares Viper ($89)
Fins - Hollis F1 "Batwing" ($180)
Computer - Atomic Cobalt II ($1300)
Mask - Tusa Freedom ($65?) as a backup mask in case the FFM fails
I've also had an Oceanic ProPlus 3 computer (belongs to my wife now) that I really liked. And Iv'e used her Atomic Z2 regulator ($450ish) and been just fine with it. I like the Hog D3 better because of the swivel. Also, with the Z2 second stage (an issue on the next tier B2 as well), if you have your hand over the front of it for any reason, it's really hard to breathe because of where the diaphragm is located. It's great reg and it breathes really nice but that's something to be aware of.
Last piece of advice I can give is this: Buy right once. Spend the money on good gear that will last. Your life depends on it.
