Consider what kind of character you want when choosing your upgrade path. If you enjoy being in the thick of battle, then focus on power and melee weapons. But, if you prefer to support other characters, then boost your spells and pace.
Hunting around the map will reveal isolated groups of enemies which can be killed to gain experience points you might have otherwise ignored.
Once a day you'll get to take part in a slot machine lottery for free, and be rewarded with currency, elixirs and other bonus goodies. Head to the Daily Reward section of the main menu to take part. You can also spend currency in this section to take another spin.
Each day, a new daily quest will be set. You might have to kill a certain number of enemies, or win a certain number of matches. Completing a daily quest will reward you with currencies and XP, so be sure to meet the objectives whenever you can to stay ahead of the competition.
Once you've entered the Talents section of the main menu, you're going to need two different currencies to advance your capabilities within each character archetype. First of all, you'll need cash to unlock new tiers of talents. Next you're going to need Talent Points which are acquired through leveling up in the game.