Long underwear: This layer wicks sweat off your skin and keeps you warm. Choose wool, synthetic or silk (not cotton). You’ll want lightweight or midweight depending on the outside temperature and whether you run hot or cold.
Light fleece or wool top: Wear it over your long underwear top in the car and the lodge; wear it under your jacket to add warmth on the slopes.
Ski or snowboard socks: Ski and snowboard socks are taller than your boots and not overly thick (thick socks can actually make your feet colder if they make your boots too tight and restrict your blood circulation). Some have padding at the shins. Go with wool or synthetic socks and avoid wearing cotton socks because, when cotton socks get wet from snow or sweat, they take forever to dry out.
Ski or snowboard jacket: These are usually waterproof or water resistant, and insulated, with convenient pockets and other snow-specific features. A waterproof/breathable rain jacket over your fleece or wool top would be sufficient as well, though its slickness might lengthen any slides you make after a fall.
Ski or snowboard pants (or bibs): Waterproof or water resistant, and insulated, these sometimes have convenient pockets, vents and features to prevent snow entering your boots. Waterproof/breathable rain pants would be sufficient as well. You can add fleece pants underneath for greater insulation.
Gloves or mittens: Choose waterproof or water resistant and insulated. Generally, greater thickness equals greater warmth, and mittens tend to be warmer than gloves, but you sacrifice some dexterity (though inner liner gloves offer versatility). You don’t need ski- or snowboard-specific gloves or mittens, but they do have some nice features, like built-in goggle wipes and long cuffs that go up to mid-forearm to keep snow out.
Helmet: Not mandatory, but highly recommended, a ski helmet helps protect your head, and it keeps your head and ears warm and dry. (Wear a warm hat if you’re not using a helmet.) Most ski resorts rent these, so you don’t have to buy one right away.
Goggles: These protect your eyes from wind, snow and glare. Check that they work with your helmet, your face shape and fit over glasses if you wear them. You want them to fit without gaps. If you don’t own a pair, see if you can borrow some from a friend for a day. If it’s not actively snowing, sunglasses are a fine substitute.
Neck gaiter or balaclava: You can pull a neck gaiter up over your nose in icy temps; a balaclava offers even greater coverage.