To help you learn how to play OverPower I need to talk about the different types of cards - good, bad, and otherwise.  Some cards are essential to OverPower and will be found in every deck.  Another group of cards may be beneficial to most players, but probably not for the typical beginner.  A third group either does not impact the game enough to worry about or you should just completely avoid altogether.
    The four most important types of cards in OverPower are Character, Special, Power, and to a slightly lesser extent, Teamwork.  You will find these in every deck and we will focus on these in building a beginner's deck.  The Character cards represent your team of four characters.  There will be a more thorough explanation of how to effectively use these cards later.  There are two types of Special cards you will use, those specifically for each of your Characters and those that may be used by anyone on your team, named Any Hero/Character cards.  Power cards are your most basic form of attack and defense.  The final card type in this group is the Universe: Teamwork card.  Teamwork cards allow two or three of your characters to make an attack on your turn which can deal a good amount of damage to your opponent.  These are the card types I think you, as a beginner, should use first.
    Some card types may be useful to the game but do not need to be in a beginner's deck.  Events, Universe: Ally, Tactic: Artifacts, and Aspects are four card types I think you can experiment with once you know more about the basics of OverPower.  Events affect both players so you need to carefully choose any you will use. Ally cards are low level attacks and require an additional card to be played so a limited number of these are ever found in any single deck.  Artifact cards can enhance your characters but are not that helpful to beginners. Aspect cards have only recently been introduced to OverPower and there are not that many of them just yet.  As you become more familiar with the rules I encourage you to experiment with these types of cards, but they may not help a beginner get started.
    There are several types of cards in OverPower that are either not recommended for beginners or are so useless that virtually no one uses them.  Mission cards rarely, if ever, affect the game and are for the more "advanced" game of OverPower, so you should ignore those for now.  The two remaining types of Universe cards, Basic and Training, are currently so useless that I will tell you to ignore those cards completely, end of story.  There is one other type of Tactic card, the Doubleshot, that barely sees more play than Basic and Training Universe cards.  I do not know of anyone who wants to use Doubleshots, but a few people have tried.  The only thing I can say about these three types of cards is that you should feel free to try them out so you will see why they do not work.  OverPower has hundreds of Characters and just about every one has between five and nine Special cards each.  Unfortunately not every character is playable and even the ones that are have some Specials that are of little use.  Of course, if you have fun using some cards that other players would not touch with a ten foot pole, I do not want to stop you.  On the other hand, you may hear about Battlesites. Battlesites give you the ability to use Character cards and their respective Special cards other than the ones that make up your team.  As a beginner I suggest that you forget about Battlesites for now and use Any Heroes/Characters, if any are available to you.  A Battlesite is one use of a Location card, the last type of card I want to talk about here.  A Location card may be used as either a Homebase or as a Battlesite.  When used as a Homebase your team must be made of four of the six characters listed on the card.  I recommend that beginners use an Any Team Location [such as Marvel Universe, Marvel Manhattan, and Omniverse] as they give you more freedom with selecting your characters.  Often, these types of cards will be tried by a beginner but I have seen them prevent a new player from learning how to play the game effectively.  Hopefully, with this advance knowledge you can skip this phase and have more fun with the game.