This will probably be my first mini jam if I can make it, but I've never actually created any music for a game. Any recommendations?

Bosca Ceoil = not bad(for begginers)

Bosca Ceoil is pretty good.

I use Beep Box, as it runs on your browser and is free.  Pretty simple. It's pretty similar to Bosca Ceoil, but without downloads. Just click buttons and it makes notes, and the UI is simple and you won't need any youtube tutorials.

If you want to go advanced, go with Musescore. It's free, but you need to register and download, and you need to know how to read sheet music. On the bright side, it also allows you to share your music, for input and as a way of publishing it. You may need a youtube tutorial though for setup. It takes longer, so I don't use it for Jams when I'm on a bad time crunch. It is much more advanced.

I recommend Bosca Ceoil it's good and easy to use

Brackeys recommended "Bosca Ceoil"

Bosca Ceoil

LMMS if you want something free but similiar to FL studio.

I suggest use some music from internet, If you don't have any experience: i doubt you can make something "ok" with bosca ceoil.

Suggestions: OpenGameArt, Evan King, and other royalty free music stuffs.

Definitely check out LMMS, it comes with some default plugins for making retro-styled tracks.

https://lmms.io/

I used audacity and converted my table beat into music

Used GuitarPro 5.0 >> to MIDI >> online converter to mp3

Good web converter with diffirent sound banks: https://www.conversion-tool.com/midi/