So are you looking to start in liquid web? Why not ask your friend what you need? Anyway in answer to your question, I would start on debian, ubuntu or centos and get familiar with virtualisation technology: for full virtualisation you can use HVM on KVM and XEN (or PV on XEN if you don't have the hardware). For container virtualisation you can look at the old BSD jails and for something more modern you can look at openvz on linux.
If you aren't too confident on the terminal, then you will need to get a bit of practice installing apache with php, installing postgres and mysql maybe nfs.
Whatever you come across while you're doing all that you sould give it a go, see what it's like because experimentation is key here.
