Be prepared
Your clothing has a big impact on your XC skiing experience so it is worth taking the time to get it right. A beautiful sunny day can change quickly into a cold, snowy blizzard so it is important to be prepared. It's not necessary to buy the latest and greatest clothing, however a little bit of planning and layering can make a big difference.
Layering
Layering is the ideal way to dress for xc skiing as you can put layers on or take them off as you need to. If you overheat and sweat too much then you get cold quickly when you stop. If the wind picks up or wet snow starts to fall a wind-proof or water-proof layer is very handy. It's very common for xc skiers to head out with a couple of layers to start off with and an extra insulating or weather proofing layer or two in a backpack just in case.
Upper body layers
First layer should be out of synthetic material or wool (not cotton) as it wicks away moisture and keeps you dry.
Mid layer can be a wool or synthetic jumper or fleece, or tracksuit or long-sleeve cycling tops.
Outer layer consists of a wind-proof or water-proof jacket (generally uninsulated in Australia).
Lower body layers
First layer can be a set of thermal pants or tights, or even both.
The next layer can be a set of tracksuit pants, thicker tights or other leggings, or cross country ski specific warm-up pants. Not jeans, as they get wet quickly and stay wet.
A final outer layer of waterproof overpants for extra warmth, wind and rain/snow protection. You may not need this, but it's to bring them in your car or back-pack just in case.
What about alpine skiing jackets & pants?
If you plan to spend time standing around or playing with kids in the snow, then the thick insulated jackets/pants generally used for alpine skiing can be a good option. However, these are not so practical if you are skiing a lot yourself, as they don't give you the option to layer up or down if needed.
Headgear
The head loses a lot of heat so this is an important bit of clothing to get right. The most common options are beanies and headbands; caps can also be used in sunny weather but they don't keep your ears warm. Beanies can be thick or thin, and it's good to have a spare dry one for after you've finished skiing. Headbands that cover your ears can also be good.
Another good option is a buff, which is very versatile and can be used to keep the neck, ears and head warm depending on how it's worn.
Eyewear
A good pair of sunglasses is necessary to protect your eyes both from the sun and reflection off the snow. For snowy conditions a protective visor is a better option, and the best solution for wet snow and/or fog is a pair of googles.
Gloves
Gloves are an integral part of your clothing whether skiing or playing in the snow. Typical gloves for tracks skiing are thin and not waterproof, they keep your hands dry and warm without overheating. For snow play or standing around, thicker insulated or waterproof gloves are recommended. A spare dry pair of gloves are always handy, especially for kids.