The only way to level, besides promos, is to do Missions.
They are listed in a how to obtain order.
Lvl 1: Starter
Lvl 2: Complete one mission WHILE LVL 1
Lvl 3: Complete one Mission WHILE LVL 2
Lvl 4: Complete 2 Missions WHILE LVL 3
Lvl 5: Complete 2 Missions WHILE LVL 4
Lvl 6: Complete 3 missions WHILE LVL 5.
Lvl 7: Complete 4 Missions WHILE LVL 6
Lvl 8: Complete 5 missions WHILE LVL 7
Lvl 9: Complete 5 Missions WHILE LVL 8
Lvl 10: Complete 6 Missions WHILE LVL 9.
When you level up, you learn the next move of your fighting set.
They are listed in a how to obtain order.
Lvl 1: Starter
Lvl 2: Complete one mission WHILE LVL 1
Lvl 3: Complete one Mission WHILE LVL 2
Lvl 4: Complete 2 Missions WHILE LVL 3
Lvl 5: Complete 2 Missions WHILE LVL 4
Lvl 6: Complete 3 missions WHILE LVL 5.
Lvl 7: Complete 4 Missions WHILE LVL 6
Lvl 8: Complete 5 missions WHILE LVL 7
Lvl 9: Complete 5 Missions WHILE LVL 8
Lvl 10: Complete 6 Missions WHILE LVL 9.
When you level up, you learn the next move of your fighting set.