Upgrading to an SSD for a speed boost?

Hello there!
I have a bit of a question regarding how I should manage my storage space between an SSD and a Hard Disk Drive.
A little background: I ended up picking up a MacBook because it’s the only machine capable of running software X.

Mostly, my setup consists of a 24GB SSD paired with a 1TB Hard Disk Drive.
Right now, both the operating system and software X—which is my main priority—are sitting on the Hard Disk Drive, leaving the SSD completely empty.

The OS takes up about 10GB, while software X needs roughly 20GB.

So, here is what I am wondering:
In an effort to optimize the actual performance of software X while I'm working, would it be smarter to install the OS on the SSD, or just the software itself? I can't fit both on the drive, unfortunately.
As it stands, my boot times are sluggish, applications take forever to launch, and so on. I suppose I could live with that, but my real goal is to speed up the actual operation of software X once it's running; I don't really care much about loading speeds.

To put it plainly, if I want to maximize the runtime efficiency of software X, should I prioritize the OS or the application for the SSD?

Thanks 👍

A 24 GB SSD?! 😂
Look, you aren't going to get anywhere with that. Just buy a decent SATA3 SSD—at least 500 GB—and install everything on it. Simple as that.

Greetings from Chicago 👍

Well, I suppose that might become an option at some point down the road.
Would you actually go through the trouble of installing an operating system or a frequently used program on it right now?

system