the car wont start unless i jiggle ground wire one the battery terminal.

When I jiggle the wire on the battery terminal the car head lights turn on. So there is power. When I go to start the car one of the wires seems to have a hole in it( the coating is stopped in assuming) it looks like the wire to the starter but in not sure. Could this be true and if so could you send me that wire diagram so I can replace it. I don't know the gauge of wire to use either. In on a very low income and in not very mechanically incline. I've done work on cars like replacing transmissions and fuel and water pumps but this is my family's main means of transportation and would really like to not mess it up. I would really appreciate any help thank you for your time!!!