Index funds are typically recommended for people who don’t want to actively manage their portfolio.
I invest my moneys thusly: 80% index funds (a variety of Fidelity and Vanguard funds) and 20% stocks of companies that I use in real life. When I come into large sums of money, after a small splurge, I invest 10% of it at a time over the course of several weeks into the same proportion of index funds and stocks to take advantage of dollar-cost averaging.
(I am aged 32 and have used this method since I was 18, though I got lucky and was able to take advantage of “on sale” stocks during the financial crisis and my portfolio was ~70% stocks and 30% index funds.)
Hope this helps a little!