A novice hunter can be shown in a snaffle but unless the show rules state they should be in a snaffle a double will more correct and is used at county level for novices.
Otherwise the usual turnout for hunters, tweed jacket, shirt and tie, cream jods etc.
The horse simple plain tack, no bling or coloured numnahs.
Show should be workmanlike and show a good gallop if the ground is safe to do so.