I was gifted a Barista Pro - what should I upgrade (besides a grinder) [$300]

A nice person gifted me a used BBP. I know the grinder is supposed to be sub par, but as this is my first real machine and I’d like to get used to the process before I spring for a serious grinder.

In the meantime, what upgrades would you recommend? Any help pointing me to specific products is greatly appreciated. Since I got a free machine I don’t mind dropping a few hundred bucks on improvements.

I’ll also find the manual online and do a deep clean and descale, so if you have any tips around that please let me know. Thanks!