Plain work man like tack. No fancy browbands etc, plain leather. You can use what bit your horse jumps best in, but obviously snaffle is preferred. Breatplates are allowed, and either unobtrusive numnah, or none at all.
Rider should be in tweed, with dark hat, smart boots/gaiters and boots, shirt and tie. Smart and workmanlike really!!
KatB is right if you are planning to compete at lower level. At county level its a little diferent but not much.
Tack should be havana, not black.
I personally dont like the no numnah thing, you can get plain dark brown ones that go with the cut of your saddle, or a dark coloured sheep skin one.
Any bit is Ok for lower/local level, but as with ridden hunter classes a double is the norm for county shows although to be fair is not compulsory and many horses go in different bits for this class.
You can do the jumping section with boots on your horse, but just make sure they are a dark colour and not too in your face.
Rider should always be in tweed jacket with gloves, shirt, tie and long boots, navy hats are the smartest and go with most tweeds.
Look at the show reports in H&H from the summer, look at what people wear in the classes you want to compete in!!!