How much liability insurance do I really need to have?

The typical answer to this kind of question is "how much are your assets worth?"

A better way to assess your risk though, is to consider that your wages can be garnished to pay off the damages from a lost lawsuit claim for however long it takes. So if you lose a large lawsuit and don't have the assets to pay it, you could be paying before your get your paycheck for the rest of your life.

For young drivers in particular, this should give great pause when shopping for auto insurance and not simply purchase the cheapest options available.

All this being said, the answer to "How much liability insurance do I really need to have?" should be:

"As much as you can afford."