You can easily do better than a factory tied Euro Nymphing Leader. While these are a fine start as you are dipping into the sport, haha, it's easy to build a leader that is more effective and more fun to fish with. Feel free to deviate as it makes sense to you.
Leader Length: 12' +/-
I have found that anglers on my guided trips and in my progression Fishalong clinics do best with a leader that is no more than about 2' longer than their rod length. A thin competition style euro line is very light, thin, and relatively stiff giving you nice connectivity to your nymphs. While a pro-competitve angler may like more mono at the tip, I think there is a balance for the civilian angler that is achieved by keeping the end of the fly line just outside the rod tip.
Basic Leader Formula:
This is not exact science, and I deviate from this build slightly but here is the jist of it. My most common variation would be running a portion of the sighter (indicator) material as 3X or 4X. Lighter is always better.