Welcome aboard!
I advise you to test your decks against a computer player before you start challenging real opponents. If you are lost in some many cards, try to build a deck around some theme you like (for example Undead).
Also you can watch replays of all the games that were recorded. This way you can rewatch your own games, but you can also watch games of more experienced players and learn from it.
If you don't understand certain card, feel free to create discussion to the specific card and ask for advice.