When two good friemds of mine started diving I got back into it after several years out of the water. They took their classes, immediately bought their own gear and saved money buying 'sets' that were configured by the store.
As I didn't have the $$$ to get all my gear I read up on it, borrowed and rented, and eventually started buying my own one piece at a time. Took me over a year, and with some of the rental gear it was a looong year. In the end I had a gear bag full of stuff that works very well and suits me perfectly. The only gear I added later were bp/w and a nitrox computer watch. Neither really necessary, but I enjoy using both.
Both friends of mine started replacing virtually their entire gear with higher quality items after trying mine, spending considerably more money on it than I did.
So no reason to hurry, if it takes a little longer to save your money do it as it will be worth it in the long run.
Like any piece of dive gear, analyze the diving you do, and that you want to do further down the road. Those are your needs. Then look at the wants. Research and try different gear and see what works for you.
In case of the BCD, for me it is a Zeagle Ranger and Dive Rite backplates with Oxycheq wing.
