Missions and Special Missions
When you start playing pay attention to to your Missions and special missions as these provide plenty of good rewards for a new player.
Legendary Card Selector
Playing the limited time special Missions will eventually give you a 'Legendary Card Selector' that allows you to pick any hero you want in the game.
Mission 5
When you reach Mission five you will get a Unique card. After you have this unique card you can determine if you want to buy the hero that corresponds with it. Having a hero and their Unique card will help make things easier.
Pack Slots
To begin with it is more beneficial to play without pack slots and focus on getting your Legendary card to the highest level as soon as possible as the higher tiers reward more cards.
Guaranteed Legendary Card
If you save 2,090 Gems you can purchase a Diamond Pack that guarantees at least one Legendary card.