Moving to Business/Law.

The mechanics of the game can be patented as long as it doesn't infringe on any existing patent and passes the requirement to registered as one. So if there is innovative mechanic that you have designed and implemented, it's worth considering.

At the moment, slot machine revenue is declining and casinos are looking for alternatives (such as VR arenas, eSports areas, etc), especially in Vegas. Even before then, it was incredibly difficult to get a new game noticed as punters tend to favour certain games even if they are very old.

I don't know what you are pitching whether it is a new type of 'slot machine' game that could have multiple themes or just the single game itself. After protecting the game and the mechanics, it might even be worth turning up at a trade event like G2E to talk to companies directly with a pitch.

The alternative is to make an app out of it. Companies like GameSys tend to do quite well out of it.

IANAL but I'm pretty sure you cant patent a game idea.

You can't copyright a game idea. You can patent the design and features of a product, which may involve game mechanics and interface features.

Thankfully in the video game world, people very rarely take advantage of this fact.

I live in Vegas, Nevada and I'm very familiar with the gambling regulations. So you're saying I should officially record down copyright? And do gambling companies have where to submit games for their consideration?

Gambling companies won't just want a game that's compliant with Nevada's regulations -- they'll want versions of it for the other 200+ gambling jurisdictions that they sell products to too.
It's not typical for an outsider to bring an idea into a company to sell it. You'd probably want to know people inside the company first, and ask them how to organize a meeting with the right people... It might not even be possible, even with the right contacts.

The game is not copyrighted yet and I'm not even sure how useful that could be, because the prospect buyer will actually be buying the idea, the concept, rather than the code per se.
I was thinking about patenting it, but the process to patent a software seems to be extremely costly and complex and I'm not sure if it's worth the pain.

If you're selling an idea, you're selling the patent, so you'll need one.
Gambling companies love patents and are locked in a cold-war against each other for ownership of ideas. When I worked at once, one of my key-performance-indicators was whether I'd submitted one idea per month for patenting -- and the same was true for the 100 other software engineers in the building.
We had a great team of patent lawyers who's job was to find the loopholes in our own patents and then iterate on the submissions until they were watertight, and also to help us find the loopholes in the competitions patents so we could freely steal their ideas.

Honestly, it's a pretty toxic industry... and then there's the gambling!

On the other hand, if you're looking for a job as a game designer as a gambling company, you could use an implementation of your idea as proof that you can do the job. They'll steal your idea and patent it for themselves (assuming it's any good to them), but you'll get a job out of it.

As well as the code, they'd also want to see the maths behind it, and that you're able to discuss key figures like the average return to player, the volatility, etc, and why they're tuned as they are.