The best way to do that absolutely is buying stocks. To be more specific I would say buying big companies stocks, their value in the long term will always increase. You can get some ups and downs but I look the charts not so close, you will see that almost everything is going up.
Cryptos could be also an option, is really easy to make more money with this, but you can lose everything, as well.
And of course, if you have enough money (not my case 🤣) you can buy properties, that always increases the price.