Hi Morgan,
A lot of times a new diver can buy new equipment for the same money as buying used equipment that will not suit his/her style of diving. This is wisdom gained from my mistakes when I first started diving and buying used gear.
If you are going to be diving locally, which I highly suggest, living in Wales probably means a dry suit is in your future. Rather than buying a full rig, start with the undergarments suitable for your waters. Rent the expensive part of the package for a while.
Next, buy a dive computer, learn what it is telling you and how to ask the questions you need answers to. This should be very high on your list of purchases. You can get good, basic, air/nitrox (I wouldn't buy an air only) computer for less than $300us new. If you decide to go with a used computer, stick with the newer models. There are a lot of used Suunto Cobras for sale and they still make them today. Problem is that a lot of the older units are starting to fail (one of mine had the pressure sensor crap out a year ago).
At this point, renting a regulator makes more sense that buying even a used one. First, I know you are hot to begin diving. We all were after finishing our OWC. Second, there are a lot of "lightly" used regulators on the market for sale by people who found they didn't dive that much for whatever reason. Even if you buy a great regulator used, at this time, you don't know enough about them to determine if they need to be serviced or not. Solution, get it serviced. By the time you get your reg back from the shop, I will bet that you could have rented a regulator for the dive season and spent far less money.
Get what you need to dive regularly and locally. When you have done that for a season or two, you will have a much better idea of the gear you need, what are good prices for used gear (I start at 1/3 online prices for used and may go up to 50%) and what to lookout for in buying used gear.
Join a local dive club, talk with as many people as possible and ask questions.
