Assuming you haven't bought one already...
Buddy wings get my vote as well. But modified:
If you're planning on diving singles, get the Tek or Travel wings so you've got the plastic backplate. Replace the webbing with one continous piece of stiffer webbing. I found the soft buddy stuff got tangled and moved around through the weight retainers, and the clips came undone.
If you're only really after using it with twins, rather than the Tekwing, get the Redwing - It's the same wing, but much cheaper. You can move the inflator hose to the left side with no problem.
Also, buy a Combro backplate (
www.backplates.co.uk) and some stiff webbing (about four meters) to make a harness with (
http://www.gasdiving.co.uk/pages/misc/kit/harness_2.htm has good harness-rigging instructions)
You'll also need to punch holes in the wing for the bolts on your twin bands to go through. Use a soldering iron for that, and finish them off with metal eyelets, available from most fabric shops or the better outdoor shops.
You've then got yourself a wing setup that'll work for any type of diving you may take up in future (with the possible exception of CDG-type dives)
You can't add a second bladder to a Buddy wing, but you shouldn't need one so long as you're using a drysuit, and you can always just buy a Redwing to have two wings.
You really do only need three D-rings if you've got pockets. If you haven't, get some pockets rather than adding D-rings, they're a great way of keeping your gear organised. I keep a spare mask, DSMB, reel, strobe, cutters, and slate in my two pockets..
HTH
Dominic