When the battery is fully charged, you theoretically have 600 watt hours available, although it's not really possible or good for the battery to drain it completely, so you might want to think of having 300-400 watt hours available at night after a sunny day.
For example, lets say you expect to run your lights for about 4 hours after dark. If you are running 6 lights bulbs at 3 watts each, this leaves you with about 230 additional watt hours. You could charge a laptop with a 80 watt charger for 1 hour, and run a 20 watt fan for 7 hours.
This all assumes that you had a day of strong sun. If it's been cloudy, you may need to conserve. Your battery's useful life and performance will be optimized if you maintain the voltage above 10.5V. If you plug in an appliance and the voltage starts to drop below 10.5, it's best to unplug the appliance until you have sunshine again.
Please note that light bulbs use very little power, so as long as you're mindful about when to plug in higher wattage appliances, you should always have enough power for lights.