Check out Equishopping's range of boots. I think it's about time we had a little guidance here as the range of boots keeps growing.
Straight away you'll see there are numerous types but lets take the minimalist approach to start with. It's all very well telling you you need x,y and z but that would make me a marketing spool rather than trying to offer advice.... For jumping most people will have a set of tendon boots. Instead of buying so called flat work wraps or brushing boots why not just wear a pair of tendon boots although they won't look as neat. Of course tendon boots can't replace XC boots which guard against all manner of grisly injuries. The same goes with fetlock boots. So it's worth paying more for a good set of tendon boots that you'll use everyday rather than cheaper boots for each separate discipline that aren't quite as good. Plus, keep it simple - why have 5,000 pairs of boots?! If you're spending more, go for decent quality leather with leather inners and clean them each day. You'll end up saving money and be better off with super supple boots. Plus, many tendon boots call themselves 'open fronted', actually they've got a mahusive strap across the front so they're not. Go for tendon boots that either have lots of thin straps across the front of have very thin webbing across the front, that way, in the nicest way possible, when a horse hits the poles they'll feel it - or else you're fighting a losing battle...
While we're on the subject of tendon boots its worth mentioning 'weighted boots'. The idea being that you work a horse and jump him in these boots with normally lead inserts and he has to work harder to go about his work. When you take them off the theory is that his legs spring up as they're so much easier to move. The juries out on that one - go discuss.
XC boots. You may have seen horses going XC in what looks like armor covering al conceivable areas of their leg they could injure. Basically with XC boots you get what you pay for, the same with saddles. However, there are certain things to look out for. Good drainage - it's not great to drop into the water and then have to carry half the water jump around the course with you . Also extra front and back leg protection on the boots is important such as carbon plates or extra padding. Especially relevant for front boots is that there's sufficient protection to the legs both on the front from fence impacts and on the rear from strikes from hind shoes to the tendons. Easy fastenings - stay clear of metal buckles. They are just too easy too get caught on legs and when they're covered in mud they're a nightmare to undo.... Velcro is better but most people tape the straps as well to prevent any untowards actions loosening them off.
Oh god, I've just suggested that you don't buy certain products! Equishopping's manager might not take this kindly... enjoy the advice while it lasts!