Gloves: Recommended, will keep your hands warm.
There are also gloves with built in wrist guards.
Goggles: Optional. Goggles will help prevent snow getting into your eyes as well as filter out the brightness of the snow on a sunny day.
Jacket: Recommended. You will want one when it is cold out, preferably with waterproofing.
Snowboarding Pants: Recommended.
Will help prevent legs from getting cold.
Pads: Optional. May restrict movement. If you are starting out you might want to wear pads as you will probably fall a lot.