Start off by hitting the switch to the right of the gate to turn off the lights and open the entrance to the casino. When you go through the gate, you'll see that there are a bunch of flashlight enemies that will shoot you on sight. It's best to just avoid them whenever there are more than one in this level, as even if you can take one out, it alerts the others. Jump through the plants on the side of the stationary guard, and grab the two bottles next to the left bank of slot machines on your way through. They move in a set pattern, so just follow behind them (but not too close), then run around the side of the last guards light while he's sweeping it the other way. Head across the laser floor bridge and take out the two bottles on the other side, then head down the hallway avoiding the spotlights until you can destroy the security alarm.
The lucky charm up in the plants show you the way to go. Follow along the ledge above the guards, jumping across the swinging sign to the next ledge until you get the two bottles up there. Jump down on top of the guards and take them out before they get a shot off so you can collect the three bottles in front of their table. Next grab the bottle on the fallen light fixture and climb the cord up to the other fixtures above. Jump across the lights, grabbing another bottle on the way, then jump down on top of the circling guard below to take him out. Run around in the plants above the slot machines behind the spinning house to collect four bottles, then grab the two on the floor behind the house. Lastly, grab the single bottle above the slot machines next to the laser floor walkway.
At the end of the walkway is a tricky bit where you'll need to jump back and forth from the middle section to one of the sides until you get a clear side to run up that is also opposite of the way the guard is sweeping his light. When you take him out, break the security alarm, then go back and take care of the four hanging bottles above the laser floor. Continue on through the hallway, where you'll take out two bottles before the card thrower and another one right after him. Down at the water, jump on the roulette table and grab two more bottles, then jump across the three roulette wheels to the next table with another two bottles on it. Jump across the tables in the water to the stairs where you'll find a safe, then continue on to the next table with another two bottles. The next three roulette wheels have lasers in some of the slots, but as long as you avoid them, it's pretty easy to just let them circle you around to the next wheels.
After breaking the security alarm, you will come to another fallen light with a cord you can climb up. Go across the lights and jump down to the table below when the guard's light is facing away so you can take him out without being shot. Grab the bottle there, then continue on. These roulette wheels add laser barriers, but since they spin away from the barriers, it shouldn't be too difficult. On the other side, break the security alarm then you'll come to the real challenge. These wheels go toward their barriers, so you'll need to jump around them in the opposite direction they're spinning while avoiding the laser slots. Just jump like there aren't any laser spots and if you're going to land in one you can use your double jump to avoid it. On the other side by the security alarm is another bottle and two more on a fallen light fixture. Climb up the cord to get the last bottle on the lights above, then jump back down where you were to input the code into the safe.
This time when you climb up the cord to the lights above, jump down on to the big spinning wheel. As Bentley will explain, you can't jump counterclockwise because the wheel is spinning to fast, so you'll have to jump against the direction of the spin. The goal is to land on the green section three times. Each time you do, it will get a little harder with the addition of extra laser slots. When you've hit it three times, the center will blow off and you can retrieve the key.