You level up by playing games and wagering, which earns you XP.
XP is awarded based on the house edge of the game you play.
The higher the house edge, the faster you earn XP.
As you earn XP, you move through the new rank and tier system.
Each time you tier up, you unlock better rewards, including 180 keys for your daily case and stronger perks.
Once you reach Corporal I or higher, you can also choose to Ascend. Ascension resets your tier in exchange for Ascension Points, which unlock permanent upgrades that make future progression and rewards even better.
In short:
Play games → Earn XP → Level up your tier → Unlock rewards → Optional Ascension for long-term bonuses.