Do I need a new starter motor? Rapid clicking when trying to jump, but no turnover.

Hi everyone! I've been googling and searching on here, and have a decent idea of what's going on, but I can't figure out if I should get a new battery or new starter motor.So, I haven't driven my 2005 scion tc for about 8-12 months or so. I know the battery has been dead for a while (somebody rummaged through my car and I didn't noticed that the interior lights were on for who knows how long). When I try to jump it, the headlights come on and all the electrical systems seem good, but I only hear a rapid clicking when turning the key. I've wiggled the cables a bit to try to get a good bite, and made sure to ground to the frame, but no luck. (also something to note is that due to the position of the car, I had to use two sets of jumper cables connected to each other to reach)My hypothesis is that if I'm jumping the car, and all the electric systems power up, it should at least try to turnover regardless of if the battery is bad (the idea being that the jump bypasses the battery). Is that correct? I was thinking of buying a new battery, but if my hypothesis is correct, then it may be the start motor. But I have also read that the rapid clicking shows that starter motor is working... any ideas? Thanks!! via /r/cars http://ift.tt/2sNzkYW