Do you supply your own Jepps on your flights or is this supplied by the company and kept on board the aircraft?
This depends on the operator. In 20+ years I haven't worked for an operator that supplied Jepps (or equivalent), though I believe QF mainline does.
How about headsets? Do you supply your own or are these fitted permamently in the aircraft?
Again it depende on the operator. My current employer provides headsets, which I find poor quality. I was using a Bose but because of security hassles and the flight deck not having a hot mic have swapped to a Plantronics MS250.
... and apologies if these questions appear naive.
At the ripe old age of 18 no questions are naive.