With the Pi: Micro SD memory card (I find 32 GB) is more than enough), HDMI monitor, keyboard and mouse. Internet connection is suggested (to download the software). That and a radio connection will get you started. The next challenge is getting the radio connected to your pi (appropriate USB cables - see your radio manual). Next is how to get the signal from your Pi into your radio. For that I use a cheap sound dongle ($4). You can find other 'sound card' devices for more if you want to spend that much: Signalink, Rigblaster, and others. The 4$ job has worked for me to get WAS QRP on 2 bands.
Next will be your software. Go the the raspberrypi.org website and download the NOOBS package and follow their great instructions. After you get the Pi up and running I suggest you do the command "sudo apt-get install synaptic". Then if you look in your preferences you will see Synaptic Package Manager. There you will find most of the software packages for amateur radio.
You did not say if your are running HF or VHF. That will let us know what other advice to give you, but if you go through the Amateur Radio programs in Synaptic you will see what if readily available without having to worry about compiling.
Then >>> Go!