Clicking is a sign of weak battery or poor connection.
That said, you may have a defective diode in the alternator that is allowing the battery to drain during long sit times.
How to test that if you do not have the tools required is, drive it around for the day like normal, then when you park it for the night, remove one of the cables from the battery.
The next morning, put the cable on. If it starts right up, then it is either a bad connection which you may have corrected by simply removing and reinstalling the cable and or a bad alternator. Actually the alternator is good from the perspective that it will charge, but with a defective diode, the current it allowed to flow back-wards through the cables.
Now,,, if it still clicks and does not start, then you need to confirm the quality of the other connections first. Tap on the starter while someone is trying the key, if it goes, then it is probably the bendix or stator within the starter, in either case, simply replace it.
Last, could be a solenoid as it basically is nothing more than an opening and closing connection kind of thing. Tap on it, wiggle the wires, that kind of thing...
Clear as mud ???????