1. Mask-Correct. Fit is important. No need to spend crazy amounts of money on this, black skirt is best. Was thinking about a clear skirt but I did do my OW in a black skirted one. Any particular reason for black compared to clear?
2. Snorkel-not needed, find the cheapest snorkel you can get if it's required for your class, then put it in the gear bin for all eternity I did my OW with a short(ish) flexible snorkel and it barely got to the back of my head (almost as soon as I went face down, I was getting mouthfuls of water. Thinking I might get a decent one as the waters here can be unpredictable and even diving from clear water could end up coming up to a swell.
3. Fins-correct, but not necessarily the way you might think. Consider your long term diving goals. If drysuit is in your future for local diving, purchase fins that will work with your drysuit. Neoprene socks under drysuit overboots work quite well for wetsuit diving and allow you to have one set of fins. Paddle fins are best, Dive Rite XT's and Hollis F1's are my favorites. For drysuits, I do not recommend integrated boots. I have had them, and have hated them. Neoprene socks are much better and can be used with either oversized regular scuba booties, or the drysuit overboots. With this system, you only need one set of fins. Hollis F1 or Scubapro Jet Fins would be my recommendation for drysuit backmount. Hadn't thought about that option having only used neoprene booties with a pair of Aqualung fins on my OW course. The DM that was along for the trip on my OW had issues with the boots supplied with his drysuit so a good point.
4. Safety equipment. Whistle and reflective DSMB if in open water. Mirror optional, but the reflective tape on the massive safety sausauges works quite well. Cutting tool. I prefer Benchmade 7 Safety Cutter, the trilobytes are good little Z-knifes too. No need for much else as you are unlikely to need to saw or pry anything, but these will cut most any line you can get entangled in. Think this will be the direction I go in - the DSMB seems like a safe choice for all diving.
5. Exposure protection. Don't skimp here, if you think you'll get into drysuits for local diving *highly recommended where you are*, just buy a drysuit.... Many courses in the UK teach basic open water in a drysuit fwiw. It's worth the investment if you're diving locally. If you are planning on diving in warmer waters regularly, then this goes to the bottom of the list. Probably mostly diving in the UK with the possibility of occasional trips abroad atm so dry suit will probably be the choice with buying a wetsuit for any trips abroad/
6. Regs. You're in Scotland, support local business, Apeks makes good stuff and are still made in the UK. Matching set is important, Apeks DST/XTX50's are my preferred set, GUE style hose routing for backmount please Worth looking at - cheers
7. BCD. Backplate and wings are the only solution if you're diving locally. You need the weight of steel, and if you're in a drysuit, they're basically impossible in a jacket style rig. Deep Sea Supply should be your only call if you are diving locally as the bolt on weight plates will be all but required for local diving. Part of this is weight system. The plates from DSS are worth it as they can be easily removed for warmer water requirements, and with a properly balanced rig there is no need for ditchable weight. Hadn't considered BP&W as I had qualified in a jacket type BCD with a harness below for additional weight (I was up at about 30lbs with the 7mm wetsuit/BCD etc)
8. Computer. One designed for decompression, preferably with a good display, multiple buttons, predictable algorithms, easy computer uploading. Shearwater Petrel is currently the standard, the SeaBear H3/T1 would be my second choice. Other than that, a used Nitek Duo/Cressi Archimede II etc *they're all the same computer made by Seiko*, can be purchased for about 100gbp and will last you a while. Nowhere near as nice as the ones above, but it's cheap and does what you really need it to. Tables and paper/excel logs work quite well though. Not sure I need a high end computer - I can't see me moving to technical diving in the near future so a fairly basic unit with Nitrox (no point in not having it even if not trained on it atm) would probably suffice although the colour computers look nice!
9. Lights. No need for big canister lights at this stage of the game unless you're doing very long dives. That said, you can find used HID's pretty inexpensively, but the small high end backup lights work well. Cave Adventurers just released the Explorer lights for just over $100 USD and are great little lights. A pair of these for OW will work well. As noted above I can't see me doing any technical diving and haven't tried night diving yet so a small light (+backup) will probably do me fine - its more for getting that little bit more light in our sometimes murky waters.
10. Cylinders. Find good diving mentors, they can likely let you borrow some so you don't have to rent.For the amount I am likely to dive, I might end up just renting for the near future.