Bitcoin is the best investment you can make for the next 30-40 years in my opinion. There are some traditional investments that are a good option for a diversified portfolio. You can buy stocks, I specifically like managed funds like the S&P500. Historically it’s done very well.
I don’t really like precious metals to be honest but each to their own. Do your own research before investing in anything obviously.
Those things can't quickly turn in to paper money. So i will put 3% my money in crypto