The coolest thing about 20k is that if you can find a way to save 2k, you've increased what you've got by 10%.

There's nothing wrong with investing an amount like 20k for a learning experience but from a returns perspective, just working is almost certainly going to be a better avenue to increase your net wealth in that range.

Investing becomes a lot more useful the further the amount you have saved becomes more removed from your earning / saving potential.