I just started doing this and i've got to say, its well worth the effort. You can probably learn more in a couple of hours messing around than you can from a week of reading.
I don't know how things work where you live but what I did was go to my local tip (dump) and asked the guy if I could take some of the old computers/parts. I had to give him a tenner to look the other way but for that £10 I have 5 working pcs in my shed on which to experiment
So I get to do some pen testing, some networking plus I can mess around with the hardware and it does not matter if I fuck something up. Win.
A wise man can learn more from a foolish question than a fool can learn from a wise answer.