What Am I Riddles

Question: What is something that you always have with you but you always leave behind?

Question: A trail, a union, together tied.
Come across me and you will find,
you cannot change the course I'm on,
without me you cannot travel on.

What am I?

Question: What small place has a lot of money?

Question: I am taken from a mine, and shut up in a wooden case, from which I am never released, and yet I am used by almost everybody.

What am I?

Question: It dances and skips,
it's read in the eyes but it cheats with the hips,
If it meets its match it's easily caught,
but it's worth nothing if it is bought.
What is it?