On the initial topic, definitely invest
If you just hold on to money, your purchasing power is constantly decreasing due to inflation
and long term investing has time and time proven its profitability (of course, along with its risks).
Diversify your portfolio
If you should recommend anyone to invest: how much of your money in savings should someone invest? How much money should someone have in order to start investing?
I think everyone should atleast have a decent buffer: an xx.xxx amount of money before they even think about investing: you should always have money to cover (unexpected) costs. Some of the long term investments do not have to possibilty to withdraw your money early.