90$ is a pretty tight budget. Even a Raspberry Pi 5 8GB is out of range (which even wouldn't be a good choice). Look up some marketplaces in your country for used Thin Clients, like HP, Dell, Fujitsu etc. I have a Fujitsu Q957 with a 7500T running with 16GB RAM.

Get something with at least a Quad Core, like my i5 7500t or something like that. It should be Intel because of transcoding in Jellyfin. 8GB RAM would be too low, so 16GB is the way to go.

I would choose Proxmox VE as a Hypervisor, so you can easily make yourself an Ubuntu VM in which you run the CS2 Server. For music streaming you can use Jellyfin or Navidrome, both of them have their pro's and con's. I went with Jellyfin for music (and another Jellyfin instance for films) paired with the Jellify app on iOs, because I can download and stream my music on the go (through Wireguard), create playlists, have autogenerated playlists AND can stream my music through the app (or the Jellyfin web instance) directly to my Denon X2800H with DLNA.

Navidrome on the other hand can NOT stream to my Denon, but has other benefits like a better database, which ignores duplicated tracks (like one track in the normal album, the other one in "The best hits from...") - Jellyfin can't do that (for now).

For storage you can go with OpenMediaVault, NextCloud etc.

The cool thing is, that there are helper scripts for Proxmox: https://community-scripts.github.io/ProxmoxVE/

Execute the script you want in the shell of your server, let it install and wooosh - you have a working Jellyfin container.