Choosing the right skis can be challenging and the marketing materials from the manufacturers doesn't help much.
Here's the way I think about it.
First choose the places you want to ski and the style of skiing that you plan to do.
Are you skiing for fitness, doing mile after mile of groomed tracks as fast as you can go?
Are you skiing for the experience of nature, venturing off track to snow filled hiking trails and rolling terrain with hills a few hundred feet high?
Are you into steep powder, seeking the thrill of downhill turns at high speeds?
Once you know where and how you'll ski, you can pick the skis, boots, bindings, and poles you'll need.
There are many types of nordic skis but for the purposes of my analysis, I'll refer to them by their typical width and edge configuration.
1. The endorphin junkie in groomed tracks - Skis less than 60mm wide without a metal edge are perfect for groomed tracks. You'll go fast on the flats. As long as the track is not too steep or too filled with turns, you'll be fine.
2. The OTBD skier (me) - Skis between 65mm and less than 80mm with metal edges are a compromise - slower on the flats but with more stability and control for ungroomed trails, turning around trees/rocks, and traversing more varied terrain in forests, streams, and hilltops.
3. The adrenaline junkie on steep slopes - Skls above 85mm with metal edges have great control for turning - telemarking, parallel turns, and stemming (letting one ski slide on the uphill side of the turn). They are slow on the flats and are too wide to be used in tracks.
You may need more than one pair of skis if you do more than one type of skiing. One size does not fit all since each ski is optimized for some types of skiing and a compromise for others.
One you've chosen your ski, you can chose your bindings.
1. For groomed track skiing, chose the New Nordic Norm T3 or Salomon Profile
2. For OTBD choose the New Nordic Norm BC Auto binding
3. For steep slopes chose the New Nordic Norm BC Magnum binding or 75mm Telemark bindings
Choose a boot that fits the binding you've selected, noting that all these binding systems are not interchangeable - the boot must be designed to accompany a specific binding type.
Poles are generally as tall as your armpits. For OTBD and steep slops, choose an adjustable length pole so you can set it longer for climbing and shorter for descending.
What do I use?
For long distances in groomed tracks - Fischer Nordic Cruiser skis, 50mm wide with NNN T3 bindings, Fischer XC Tour boots, and Fischer XC Sport poles - generally about $250 for the package.
For OTBD skiing - Fischer Outbound Crown, 70mm wide with a metal edge and NNN BC Auto bindings, Fischer BCX 6 boots, and Fischer BCX poles - generally about $500 for the package.
Of all the websites with educational materials about Nordic skis, the most useful I've found are the videos at Onion River Sports and an older collection of pages called Dave's Backcountry Skiing page.
I hope this overview is helpful. Let it snow!