Accounts in Vegas World level up based on their wagering. The larger and more frequent your wagers, the faster you advance. Currently Vegas World levels go up to 60, and each level is a bit harder to reach than the one before it. With even modest wagering, players can expect to level up quickly at first, then things start to settle down when you get into the upper teens.
Playing the Vegas World slots games are, generally speaking, the fastest way to level up. The sheer number of Coins a player can wager playing slots far exceeds any other Vegas World game, even the games with far higher betting limits. The risk of losing your Coins wagering in this manner is also greater, so be careful!
Don't get too hung up on leveling up. It unlocks Dance Moves and Suite Themes, and that is all. The Loyalty Rewards program is where you can earn all the fancy prizes and bonuses.