Tank601
Contributor
Those shorts are nice but pricey!

If you look for a package online you can get everything you need for $200-$300. Though this will be the most basic variety (which some divers prefer). My second BP/W setup was this: TECHNICAL SCUBA BCD PACKAGE @ Divers-Supply.com . My first was a larger brand name and about twice the price. Both are pretty close in apparent build quality.
For any single tank setup you need to be sure you have at least
- backplate - Aluminum or kydex for warm water
- harness - basic Hog harness works well
- crotch strap - very helpful to keep the backplate in position, especially on the surface
- wing - get a singles wing for a singles tank
- cam bands - most often you need two
- Single tank adaptor - Optional with some BP/W combinations, but often recommended anyway.
- d-rings, Belt Buckle, belt slides - Stainless steel preferred, these will often come with the harness.
For pockets, I agree with a number of others on the board that pockets glued to your wetsuit (drysuit for me) are better than pockets that attach to the BP/W. You can add pockets to the waist band on a BP/W, but it is often easier to use pockets on your thigh. There are also shorts that you can wear over your suit with attached pockets (for example, XS Scuba Highland Neoprene Pocket Shorts - Dive Right In Scuba - Plainfield, IL). I've never had to try these myself.