After calculating and building your emergency fund, your extra money is best put in investment, assuming you already have the proper knowledge to evaluate the risk you are taking. If you just put your extra money in a cash account which earns very little in interest then you are not maximizing its potential. You are also losing the value of your cash and its purchasing power due to inflation.
For common job positions, there’s a limit to how much salary and increases a person can get. However, the room for making money from investments is so much larger. So the more money you can put in investment the better your chance of increasing your income in the future compared to the salary increases you will get.
Before putting your money in any investment, make sure that you have the right knowledge and enough information to make the right choice. You can’t just put your money in any investment and assume that it will grow. Remember that reward is directly proportional to risk so if you know nothing about the investment then your risk becomes very high which translates to very high chance of you losing your money. So read through these notes and gain as much knowledge as you can about investing before doing it.