Answer:
Curtail me thrice I am a youth; behead me once a snake; complete I'm often used in truth when certain steps you'd take.
You can see it everyday, but cannot touch it at will. What is it?
I am the beginning of the end and the end of time and space. I am essential to creation and I surround every place.
I'm a precious stone in a pack of cards. What am I?
A large oasis in the desert. Come with cash and leave with none. What am I?
No matter how little or how much you use me, you change me every month.