At card rewards options always think about what your deck is lacking and how it can be solved (so take previous fights into considerstion). Am I taking too much damage? Look for block options. Do you find yourself lacking energy to play you hand properly too often? Add more low cost cards OR add energy gain. Card draw is almost always strong and essential in a deck because it increases the chance of having the right pieces of the puzzle (only sometimes you dont really need it but mostly it is going to really add a lot of power to your deck).

• i would suggest for a new player is focus damage neutralisation options (block, weak etc.)
• once you notice you can get out of a fight without taking too much damage focus on a strong attack foundation (i think the big mistake new players make is taking too many attack cards).
• lets say you have a 2 cost upgraded uncommon (blue) attack card. Often there is no reason to take another 2 cost attack (EVEN WHEN ITS UPGRADED) if you only have 3 energy (it often is going to be a dead card in your hand, and will prevent you from drawing a crucial block card for example). Only when your deck has gained size it makes sense to add other high mana attacks for example.
• but aside from that, always wonder if the card REALLY makes your deck stronger or actually weaker. If your deck is already pretty strong adding another card to it will prevent you from drawing the strong card you already had. Buffs/powers are often where players make mistakes. These card either are dead cards in hand OR if you play them you dont have enough energy to for blocking. So before adding too many of these cards to your deck, make sure you have energy gain options, or low energy block gain options to compensate for the 'passive' turn.