Teleportation and circles

1) You can create a teleportation circle using regular ritual components that are found in any half decent arcane shop but without the spell 'teleportation circle' it will lose its potency quickly based on the skill of the person inscribing it, a matter of hours or days (this is the house rule)

2) once you have that spell you can travel to any circle that you know the sigil sequence of, you don't need to cast it at an already existing circle

3) since it is a 5th level spell you would need to find a scroll of the spell (2 i expect, to get in and to get out) to be able to cast that spell unless you want to hang around till you can cast 5th level spells