Since you are just starting out, I would avoid spending lots of money if you can. It's just not necessary at this stage. You can set up a virtual machine environment on a single computer using freely available software such as VirtualBox. This will also allow you to run multiple VMs of different flavours on a host-only network, so they cannot be interacted with on your home network. In terms of other hardware requirements, it would depend on the sort of stuff you want to learn. For example if you were going to study WiFi, you will probably want a USB card such as the Alpha AWUS036H and an access point to test with.
In time, you may want to buy other bits of kit to play with, but I suspect that will be quite far in the future Walk before you can run