Short answer : read the datasheet of the LDR
That should have values for its resistance in dark conditions, but I'm not too sure how to convert datasheet info to its "full sunlight" resistance. Best to take it outside on a sunny day with a multimeter. uk full sunlight varies somewhat between 700 and 900 Watts per square meter. Datasheet test conditions tend to prefer 1000 W/m^2 though they might show a chart or table.
I can't track the direction of variably bright sunlight with only one sensor but do record the signal indicative of the brightness of it landing on a scrap garden lamp 2V 3mA photovoltaic cell into a 270 Ohm resistor (smaller resistor to get <2V) and that provides a suitable analog volage for one of the "a0" analogInput pins. I'll write that up if requested to., as the arduino a/d values might be closer to linearly dependent on sun power than what you are working on.