I've got plans for a series of posts outlining some basic gear-buying advice, but before I give specific recommendations, I'd like to lay out some basic points about my general approach to buying roller derby equipment.
Fit Comes First
I can write about durability, performance, and materials quality, but ultimately what decides whether a piece of gear is right for you is whether it fits the shape of your feet, legs, arms, or head. Your boots, pads, and helmet should all fit as snugly as possible without causing pain, numbness, or pressure points. Different gear manufacturers do their best to provide consistent sizing, but you might find yourself between a Medium and Large in one brand while another's Medium fits perfectly, so you should shop around until you find something that fits.
The best skates in the world won't do anything for you if they're a size too big, and no knee pads will protect your knees if they keep sliding down your shins. Whenever possible, you should buy gear that you know will fit snugly and comfortably.
Of course, this assumes that you have the chance to try something on before you buy, which is one of the reasons you should...
Buy Local If You Can
We're all lucky enough to have a number of different places we can choose to buy our skates, pads, and wheels from, but I think that if you have the option to buy from a local, derby-focused skate shop, you should. It's good for the skater to be able to try stuff on and receive specific advice, and it's good for the sport to support the network of shop owners that have a vested interest in the long-term growth of the sport.
There isn't yet a retail derby gear shop in every village and hamlet, but if you live within a day's drive of Austin or Phoenix or Eugene or Seattle or the Bay Area or NYC or Upstate or New England or Chicago or Saint Paul or Atlanta, then I recommend making the trip. Lots of these are small shops so if you do have a long drive to get there, I recommend calling ahead and confirming their hours for the day you plan to visit.
Many of these shops also set up vendor tables at tournaments, so if you have an event coming up near you, that might be the next best thing. Coordinators of the tournament should be happy to tell you what gear vendors, if any, will be in attendance. If you go, it's best to hit the vendor area early and get first pick of their available stock.
If neither of those are options, it might still be a good idea to order from one of the online stores of those derby-focused merchants. Email conversations on size and selection aren't as good as in-person advice, but it's better than you'll get at Amazon.
Don't Cheap Out On Safety
I've already said my piece about why you should buy a certified helmet, but I think that the idea of investing in good safety gear applies more generally. The right set of pads for you might not be the most expensive, but you should pay what you need to in order to get pads that fit with generous protection and padding.
This means that you should replace any pads that are stretched out or coming unstitched or failing in any other way to live up to their full protective potential. Also, I'm skeptical of getting safety gear second-hand, especially knee pads and helmets. I understand the impulse to save a few bucks, but roller derby is a contact sport and taking it seriously means taking every reasonable step to reduce your risk of injury.
Plus, not to be a downer but even the most expensive pads are a whole lot cheaper than a concussion or a broken bone.