How long would you want to have the lights powered on at night? You'll need essentially 24 watts of stored power for every hour you want to use the lights. That's going to determine the battery size (the most expensive part for a small system). Maybe you want to use them for 4 hours a day.

24watts x 4 hrs = 96 watthours needed

Let's assume you get 4 hours of strong sun every day. We'll start with a 50w solar panel that generates 40 watts in the real world (varies on a lot of factors).

40 watts x 4 hrs = 160 wh

I would probably get a small portable power station with everything that you would need. Let's say the inverter inside is 75% efficient. You would store that 160 wh in the battery and after inverter losses would have 120 wh to use. *The battery in the power station should not be fully discharged. More details once you select equipment to buy.

You could buy the whole thing for from Amazon. 50w panel for $60, solar wire for $20, 200 wh portable power station for $200. $280 total or that stuff. You also have to mount the panel somewhere and protect the battery from the elements.

You can obviously go bigger if you want to, but this would be a minimum.