Answer:
I am one small little piece of paper yet sometimes hold lots of value. I am all you need to get in to big events but will cost you. I am an important part of travel. And if lost you're not coming.
I am bought by the yard but worn by the foot
I can point in every direction but can't reach the destination by myself. What am I?
I have a ring but no fingers. I used to stay still all the time but nowadays I follow you around.
I hide but my head is outside. What am I?
No matter how little or how much you use me, you change me every month.