In hand showing attire is generally the older style, e.g. for a welsh or english breeds, new england etc, they often wear a nice outifit consisting or show pants, a nice hsirt and a med brim hat, lace and runnign shows, (not joggers) but i think your meaning the english attire, as in jod purs and shirt and tie
For starters, i would get a nice pair of beige jodpurs, and a light shirt, the shirts come in two styles.
1. Collar- which you wear with a matching tie
2. Rat-cathcer- which you wear with a stock pin
both are nice, rat-cathcers are generally more expensive.
Next, the jacket, many shows insist on jackets, but they are usually not compolsary, match with your shirt, but usually a darb blue, a black or a grey, maroon is not suitable.
Boots: Short boots are recommended for pony classes, but for adult classes, long boots are best. you should look like an adult, where as children shouldn't look grown up.
If you attend the first show and your not wearing teh right attire, tahts ok, compete and take not. They may be wearing anice show out fit, consisting of a pair of show pants, and a nice tucked in shirt. And a lacey wide brim hat.
hope this helps