Career is a long-term challenge that includes fan boost, exclusive Legendary Characters, and Accessories as well as rewards such as Gold, Diamond, and Packages. When you complete career mode, you get a total of +1000% fan boost for all matches.
You can obtain Career Tickets from Player of the Match, Daily Login Rewards, Scratch cards, free rewards, and by purchasing with diamond. Career matches require more tickets as you progress in your career.
You can play on Career mode by using Career Tickets and obtain the current career rewards for each win as well as EXP, Fans, and Gold.
To be able to continue on your career journey, you have to surpass certain Power Milestones. Power is basically the sum of all your characters' current powers. You can increase your total power by improving your roster and gain access to exclusive legendary characters and accessories.
Note: If you cannot find an opponent for a career match, your tickets are returned but you have to close and reopen the game to update the ticket count.