You will not be earning any XP like in previous Madden NFL Mobile games by simply playing in events. In Madden NFL Overdrive there are currently only three ways you can earn XP to level up and as you can see from the list below it makes personal leveling and progression slow.
Daily Objectives
Completing your Daily Objectives.
Achievements
Completing Achievements.
Overide Mode
Winning games in Overdrive mode.