I bought S&P when it was <$2000 and have added ever since. You get a lot of diversity with 500 stocks. SPY is the symbol
However, the top 10 stocks account for 21.8% of the value of SPY. They also account for most of the increase over the last several years. Six of them are tech stocks, and the seventh, Berkshire Hathaway, has a lot of Apple stock itself.