Index. 就和買一杯咖啡一樣簡單，嗬嗬

Despite the array of choices, you may need to invest in only one. His Royal Investment Highness Warren Buffett has said that the average investor need only invest in a broad stock market index to be properly diversified.

Vanguard’s Total Stock Market Index Fund (VTSMX) 

https://www.nerdwallet.com/blog/investing/simple-portfolios-for-retirement-goals/