1980 Questions for all other cars Intermittent Starting

1980 310 Datsun.

When I try to start my car, It sometimes takes 2-5 minutes to get it to start.

I put the key in and try to turn on the car and nothing happens. If I leave the key to ACC(accessories) the accessories will work.

I have looked in the user manual and it tells me that if the CHG light is faint it could be a high electrical load.
It also says if the light is not on it could be an electrical systems failure somewhere.

I can not tell if the light is just getting over flow from the light next to it (which is supposed to come on.) Or if it is faintly lit.

I can hear a 'click' as if something is turning over however there is no engine start. It sometimes takes many attempts to start the car.

I received this car as a gift just recently from a family friend as my first car and I want to keep it as long as possible. I have been told everything from alternator to starter to ignition.

I know very little about cars.

Not sure how long ago the spark plugs or battery was changed, but everything was working fine until recently. The problem seems to be getting worse.

Anything you can do to help would be appreciated!