The game really hits the ground running, which is great in the context of a game jam where people mostly want to hop in and get to the action. However, if you were to develop this further, I think the game would benefit a lot from a much slower start! Have only one room with 2 or 3 slot machines and a few dedicated customers, and then you have to buy additions like more slot machines, poker tables, more rooms, etc. That slower start would allow for an incremental tutorial and generally help the player not get overwhelmed, as well as make balancing things a bit easier. So many customers and slots off the bat means you don't have to do much to be profitable, and while it's fun to see the number go up, having no threat of failure is a little boring.
I can imagine a ton of depth that could be added to the management of your employees too - maybe some are better at their jobs than others and start off more expensive, but the ones that are worse might improve over time for a lower salary.
You did a great job for your first submission to a jam, though! It's a cute little simulator, and I'd love to see you expand on it!