We've taken you through the basics of Magic Duels and provided a quick primer on beating the story mode. Now here's a handy video guide to get the most out of multiplayer: not just the ins and outs of various modes, but also some core principles for deckbuilding.
There's no substitute for drawing the right card at the right time, but you'll have a lot more success if you properly craft your deck from the outset. Here's Junglist once more, with a three minute walkthrough on general multiplayer strategy. There's also a great guide on putting together a simple deck with starter cards that can help you cleave through Planeswalkers online.