If it doesn't even crank and no lights work, don't waste your time on the ignition system. Start by measuring the battery voltage. It will be 12.6 volts if it's fully charged. If it is charged, move your meter probes from the battery posts to the cable clamps, then down the wires until you find where you lose that voltage. That will be the point of the bad connection.
Be sure the smaller negative battery wire is bolted solidly to the body. Follow the positive cable to the starter solenoid. It attaches to one of the larger terminals. That is the one that some smaller wires will also be attached to. There should only be one fat cable attached to the other large terminal. It goes down to the starter.