This varies depending on the power of the appliances you wish to use.
As a general rule I would say this
1. Install at least 2 leisure batteries, as a 12v fridge will use a fair bit of power, as 1 battery wont be enough. You might want to consider 3 batteries if you will use the laptop a lot.
2. Install a batter-to-battery charger, or split charge relay to ensure the leisure batteries charge when the engine is running, as this is a much faster charger than solar.
3. Solar panels are fairly cheap now. Get as many as will sensible fit on your roof.
I lived in my vehicle, using a laptop a lot.
I had 3 x leisure batteries and a 12v fridge, 180w of solar.
It was just enough. Sometimes not quite enough.
8 years later I still have the same fridge and solar panels, but have replaced with a single battery as the vehicle is only used occasionally.