I have a 20lb barbell, what's a good basic starting workout routine?

I am a 6'1, 150lb individual who can be accurately described as both "skinny" and "scrawny".

I am considering purchasing a set of weights but want to make sure that this is something I will stick with before forking out the cash.

I currently own a 20lb barbell and am curious as to what would be good for someone just starting. (What exercises, how many, how often, etc.)

Thanks!