Go for a BP/W first. I know this has been overkill but its true. My order would be
BP/W-
With my GUE group I have seen everything from Halcyon to HOG. BP I would get used anywhere you can, go stainless. A plate is a plate and will last a long time. The HOG plates are similar to dive rites and Hollis is similar to Halcyon/Scubapro. Harness look into the Dive rite or light monkey basic harness you only need 2 shoulder D rings, 1 left hip, scooter ring, and the butt d ring. Both are simple with a precut grommet in the middle making threading and screwing in bolts easy. A single tank wing should not need more than 35lbs of lift. I can dive my drysuit and steel 119 and still float the rig with weight belt attached to it if needed and I can still use that same wing with a 3mil shorty and an ali 80 in the Caribbean and not have it taco. Important thing with wings, stay away from bungied wings. A doubles wing typically comes in 40-45 and 55-60 lbs. Figure out your weighting and lifting requirements but most likely you will not need a 60lb lift wing for a while. I'd go with a doughnut style wing if possible, don't have to worry about moving gas around in the wing.
Regs-
Make sure the second stages are downstream valves (stay away from Poseidon's, Mares, and the Hollis 500SE other Hollis regs are fine) diaphragm or piston first stages does not matter. Again I've seen everything from HOG D1's to Scubapro A700's. I personally use Apeks XTX50's. If going for a diaphragm style and diving doubles go for a 5th port addition as it make hose routing a lot easier. Wear a 7 foot hose and a 22-24 inch bungied backup, typically most people go with the same backup second stage as their primary second stage. The SPG is 2-2.5 inch diameter brass and glass on a 24-26 inch HP hose, bolt snapped to the left hip D ring.
Backup lights- Keep it simple best thing I've found is the DIRS 1000 lumen. That thing is a tank.
Can light-
this is your communication tool underwater, allows you to see more and keeps a hand free. You decided on LED or HID, Im going to disagree with Dr. Lecter on the power needed. 10W LED is enough power to start with or 18W HID. Halcyon HID bulbs are fairly fragile compared to other brands. LED is simpler than HID. Also used for storing the long hose under normal use.
Hope this helps!
GC