There are several ways in which you can obtain more heroes in Grand Chase Mobile. Although most of the heroes you get will be useless in the long run they can still be used for fusing to get a higher ranked hero or turned into Prana by selling them.
One way new characters can be obtained is through summoning. This is done by going to the main screen of the game and tapping the shop icon and choosing to summon heroes which will then present you with three options:
Premium Summon:
Premium Hero Ticket is required
Rare Hero Summon:
Spend Gems
Monster Card:
Spend Gems
Although you will get more heroes from other areas of the game you will discover that the rare ones are cheaper at the shop and you also get free Summons regularly. Completing missions in the Adventure mode will reward you with more heroes and there are plenty of in-game stores such as the Prana Shop and Guild shop that can give you tickets to purchase rare heroes. Another option is participating in the special events and of course there are all the battles that can give you more heroes.