Hello and welcome.
We've chatted about this topic before. Here's one of the threads. Does my horse need protective boots
As well as some of the research behind boots: Boots vs Polos .... Here is the Professional's Choice SMB study from 1998 ...
Basically, the brand and type of boots is all personal preference of the rider.
I myself prefer to use Professionals Choice SMB 3 sport boots on all four legs, and Classic Equine bell boots on the front legs.
Some people prefer Classic Equine Boots. Some prefer Iconoclast. Some Pro Equine. They are all good quality brands; just different preferences.
Some people prefer to use polo wraps, which is fine too. However, do NOT use polo wraps unless you know exactly how to wrap them. If they are wrapped wrong they can cause serious tendon and ligament damage to your horse's legs, or come undone during a run.
Most people do not use skid boots on the back legs for barrel racing, unless you've got a horse that really slides into the turn. I've seen them used, just not commonly. Usually you'll see a sport boot or polo wrap.
And some people use nothing on their horse's legs. I myself don't go for that, because I feel like the boots at least provide phsyical protection from a leg hitting another leg. The boots are much cheaper to replace than horse flesh or a vet bill.
Sorry. There is a good chance you are going to spend WELL over $70. Do not buy the cheap no-name boots. They do not fit well and they do not last. A good quality set of sport boots will last you YEARS. I still have one of the first pairs I bought and they are almost 10 years old. I've have taken good care of them over the years, and so they hold up.